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Purpose To investigate the association of meal timing with body composition and cardiometabolic risk factors in young adults. Methods In this cross-sectional study participated 118 young adults (82 women; 22 ± 2 years old; BMI: 25.1 ± 4.6 kg/m2). Meal timing was determined via three non-consecutive 24-h dietary recalls. Sleep outcomes were objectively assessed using accelerometry. The eating window (time between first and last caloric intake), caloric midpoint (local time at which ≥ 50% of daily calories are consumed), eating jetlag (variability of the eating midpoint between non-working and working days), time from the midsleep point to first food intake, and time from last food intake to midsleep point were calculated. Body composition was determined by DXA. Blood pressure and fasting cardiometabolic risk factors (i.e., triglycerides, total cholesterol, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, and insulin resistance) were measured. Results Meal timing was not associated with body composition (p > 0.05). The eating window was negatively related to HOMA-IR and cardiometabolic risk score in men (R2 = 0.348, β = − 0.605; R2 = 0.234, β = − 0.508; all p ≤ 0.003). The time from midsleep point to first food intake was positively related to HOMA-IR and cardiometabolic risk score in men (R2 = 0.212, β = 0.485; R2 = 0.228, β = 0.502; all p = 0.003). These associations remained after adjusting for confounders and multiplicity (all p ≤ 0.011). Conclusions Meal timing seems unrelated to body composition in young adults. However, a longer daily eating window and a shorter time from midsleep point to first food intake (i.e., earlier first food intake in a 24 h cycle) are associated with better cardiometabolic health in young men. Clinical trial registration NCT02365129 (https://www.clinicaltrials.gov/ct2/show/NCT02365129?term=ACTIBATE&draw=2&rank=1).

Purpose Metabolic flexibility (MetF), which is a surrogate of metabolic health, can be assessed by the change in the respiratory exchange ratio (RER) in response to an oral glucose tolerance test (OGTT). We aimed to determine the day-to-day reproducibility of the energy expenditure (EE) and RER response to an OGTT, and whether a simulation-based postcalorimetric correction of metabolic cart readouts improves day-to-day reproducibility. Methods The EE was assessed (12 young adults, 6 women, 27 ± 2 years old) using an Omnical metabolic cart (Maastricht Instruments, Maastricht, The Netherlands) after an overnight fast (12 h) and after a 75-g oral glucose dose on 2 separate days (48 h). On both days, we assessed EE in 7 periods (one 30-min baseline and six 15-min postprandial). The ICcE was performed immediately after each recording period, and capillary glucose concentration (using a digital glucometer) was determined. Results We observed a high day-to-day reproducibility for the assessed RER (coefficients of variation [CV] < 4%) and EE (CVs < 9%) in the 7 different periods. In contrast, the RER and EE areas under the curve showed a low day-to-day reproducibility (CV = 22% and 56%, respectively). Contrary to our expectations, the postcalorimetric correction procedure did not influence the day-to-day reproducibility of the energy metabolism response, possibly because the Omnical’s accuracy was ~ 100%. Conclusion Our study demonstrates that the energy metabolism response to an OGTT is poorly reproducible (CVs > 20%) even using a very accurate metabolic cart. Furthermore, the postcalorimetric correction procedure did not influence the day-to-day reproducibility., Spanish Ministry of Economy and Competitiveness via Retos de la Sociedad grant DEP2016-79512-R, European Commission, Spanish Government FPU15/04059 FPU19/01609, University of Granada Plan Propio de Investigacion 2016-Excellence actions: Unit of Excellence on Exercise and Health, Junta de Andalucia, Consejeria de Conocimiento, Investigacion y Universidades via the ERDF SOMM17/6107/UGR, Fundacion Alfonso Martin Escudero, Universidad de Granada/CBUA

Purpose: Brown adipose tissue (BAT) increases metabolic heat production in response to cold exposure. Body size and composition are involved in the human cold response, yet the influence of BAT herein have not fully been explored. Here, we aimed to study the association of the cold-induced shivering threshold time with body composition, BAT, the perception of shivering and skin temperature in young adults. Methods: 110 young healthy adults (81 females; age = 21.7 ± 2.1 years, BMI = 24.2 ± 4.3 kg/m2) underwent 2 h of individualized cooling, followed by the quantification of BAT using a18F-fluorodeoxyglucose ([18F]FDG) positron emission tomography-computed tomography (PET-CT) scan. Body mass index (BMI), lean mass, fat mass and body surface area (BSA) were also measured. Shivering threshold time was defined as the time until shivering occurred using an individualized cooling protocol. Results: The shivering threshold time was on average 116.1 min for males and 125.8 min for females, and was positively associated to BMI (β = 3.106; R2 = 0.141; p = 0.001), lean mass (β = 2.295; R2 = 0.128; p = 0.001) and fat mass (β = 1.492; R2 = 0.121; p = 0.001) in females, but not in males (all p ≥ 0.409). The shivering threshold time was positively associated with BSA in males (p = 0.047) and females (p = 0.001), but it was not associated with BAT volume or [18F]FDG uptake nor with the perception of shivering and skin temperature perception in both sexes. Conclusion: The shivering threshold time is positively associated with whole-body adiposity and lean mass in females, but not in males. The shivering threshold time was positively associated with BSA, but no association was observed with BAT nor with the perception of shivering or skin temperature. Future research should consider the influence of body composition when applying cooling protocols among individuals with different phenotypical features., Spanish Government PI13/01393 PTA 12264-I, Retos de la Sociedad DEP 2016-79512-R, European Commission, Spanish Government FPU 13/03410, Fundacion Iberoamericana de Nutricion (FINUT), Redes Tematicas de Investigacion Cooperativa RETIC Red SAMID RD16/0022, AstraZeneca, University of Granada Plan Propio de Investigacion 2016 - Excellence actions: Unit of Excellence on Exercise and Health (UCEES), Plan Propio de Investigacion 2018: Programa ContratosPuente, Junta de Andalucia, Consejeria de Conocimiento, Investigacion y Universidades (ERDF) SOMM17/6107/UGR, Fundacion Carolina C.2016-574,961, Fundacion Alfonso Martin Escudero, Ministerio de Universidades y la Union Europea-NextGenerationEU RR_C_2021_04

In rodents, exercise alters the plasma concentration of exerkines that regulate white adipose tissue (WAT) browning or brown adipose tissue (BAT) metabolism. This study aims to analyse the acute and chronic effect of exercise on the circulating concentrations of 16 of these exerkines in humans. Ten young sedentary adults (6 female) performed a maximum walking effort test and a resistance exercise session. The plasma concentration of 16 exerkines was assessed before, and 3, 30, 60, and 120 min after exercise. Those exerkines modified by exercise were additionally measured in another 28 subjects (22 women). We also measured the plasma concentrations of the exerkines before and after a 24-week exercise programme (endurance + resistance; 3-groups: control, moderate-intensity and vigorous-intensity) in 110 subjects (75 women). Endurance exercise acutely increased the plasma concentration of lactate, norepinephrine, brain-derived neurotrophic factor, interleukin 6, and follistatin-like protein 1 (3 min after exercise), and musclin and fibroblast growth factor 21 (30 and 60 min after exercise), decreasing the plasma concentration of leptin (30 min after exercise). Adiponectin, atrial natriuretic peptide (ANP), beta-aminoisobutyric acid, meteorin-like, follistatin, pro-ANP, irisin and myostatin were not modified or not detectable. The resistance exercise session increased the plasma concentration of lactate 3 min after exercise. Chronic exercise did not alter the plasma concentration of these exerkines. In sedentary young adults, acute endurance exercise releases to the bloodstream exerkines that regulate BAT metabolism and WAT browning. In contrast, neither a low-volume resistance exercise session nor a 24-week training programme modified plasma levels of these molecules.

Funding for open access charge: Universidad de Granada/CBUA. This study was funded by the Spanish Ministry of Economy and Competitiveness via the Fondo de Investigacion Sanitaria del Instituto de Salud Carlos III (PI13/01393), by the Retos de la Sociedad program (DEP2016-79512-R), European Regional Development Funds (ERDF), the Spanish Ministry of Education (FPU13/04365), the Fundacion Iberoamericana de Nutricion (FINUT), the Redes Tematicas de Investigacion Cooperativa RETIC (Red SAMID RD16/0022), the AstraZeneca HealthCare Foundation, the University of Granada Plan Propio de Investigacion 2016-Excellence actions: Unit of Excellence on Exercise and Health (UCEES)-and Plan Propio de Investigacion 2018-the Programa Contratos-Puente and Contratos Perfeccionamiento de Doctores, the Junta de Andalucia, Consejeria de Conocimiento, Investigacion y Universidades (ERDF; ref. SOMM17/6107/UGR), and the Fundacion Alfonso Martin Escudero (grant awarded to GSD)., Thyroid dysfunction is associated with classic cardiometabolic risk factors in humans. However, this relationship remains unclear in young euthyroid adults. The present work examines the associations of circulating thyroid hormones (THs) and thyroid-stimulating hormone (TSH) concentrations with body composition and cardiometabolic risk factors in young euthyroid adults. A total of 106 sedentary, euthyroid adults (72 women; 22 ± 2 years old) participated in this cross-sectional study. THs and TSH serum concentrations were determined in fasting conditions (6 h). Body composition (fat mass (FM), lean mass (LM), and visceral adipose tissue (VAT)) was determined by dual-energy X-ray absorptiometry, anthropometric parameters (weight, height, and waist circumference) were measured, and neck adipose tissue mass was quantified through computed tomography (CT) scanning. Cardiometabolic risk factors including fasting glucose and lipid metabolism markers, hepatic phosphatase and transaminases, and blood pressure were also assessed. Free triiodothyronine (FT3) concentration was positively associated with body mass index, LM, VAT, and waist circumference (all P ≤ 0.038). FT3 was also associated with glucose, insulin, HOMA-IR, fatty liver index, and blood pressure (all P < 0.024). All the associations were attenuated when adjusting for sex. In contrast, we found no associations of TSH or free thyroxine with any body composition parameter or cardiometabolic risk factors. In conclusion, FT3 is associated with central adiposity and cardiometabolic risk factors including insulin resistance, fatty liver index, and mean, systolic and diastolic blood pressure in young euthyroid adults. ClinicalTrials.gov identifier: NCT02365129., Universidad de Granada/CBUA, Spanish Government PI13/01393, Retos de la Sociedad program DEP2016-79512-R, European Commission, Spanish Government FPU13/04365, Fundacion Iberoamericana de Nutricion (FINUT), Redes Tematicas de Investigacion Cooperativa RETIC Red SAMID RD16/0022, AstraZeneca, University of Granada Plan Propio de Investigacion 2016-Excellence actions: Unit of Excellence on Exercise and Health (UCEES), Plan Propio de Investigacion 2018-the Programa Contratos-Puente, Contratos Perfeccionamiento de Doctores, Junta de Andalucia, Consejeria de Conocimiento, Investigacion y Universidades (ERDF) SOMM17/6107/UGR, Fundacion Alfonso Martin Escudero

Purpose of review The prevalence and burden of obesity has reached alarming levels. The assessment of human energy expenditure enables the identification of obesity-prone and obesity-resistant individuals and helps to explain the short and long-term success of weight loss treatments. In this review, we describe the state-of-the-art methods used in the assessment of human energy expenditure and the impact of dietary intake on the interpretation of the data. Recent findings The reference techniques to assess energy expenditure in humans have not significantly changed during the last century. Today, indirect calorimetry, either using a metabolic chamber or a metabolic cart, is the favored method to assess human energy expenditure and is the only method enabling the assessment of macronutrient oxidation. The doubly labeled water method however provides accurate assessment of human energy expenditure under free living conditions. Summary Although energy expenditure and macronutrient oxidation can be assessed by simple calculations from oxygen consumption and carbon dioxide production, these calculations can provide erroneous results or require corrections and/or more complex interpretation when several biochemical pathways are simultaneously engaged. Such physiological mechanisms are often elicited by dietary interventions including, among other, gluconeogenesis, lipogenesis, ketogenesis, alcohol oxidation and under or overfeeding.

Supported by the Spanish Ministry of Economy and Competitiveness via Fondo de Investigación Sanitaria del Instituto de Salud Carlos III grant PI13/01393 (to JRR), Retos de la Sociedad grant DEP2016-79512-R (to JRR), and European Regional Development Funds (ERDF); Spanish Ministry of Education grant FPU13/04365 (to GS-D); the Fundación Iberoamericana de Nutrición (to JRR); Redes Temáticas de Investigación Cooperativa grant Red SAMID RD16/0022 (to AG); the AstraZeneca HealthCare Foundation; the University of Granada Plan Propio de Investigación 2016—Excellence actions:Unit of Excellence on Exercise and Health (to JRR)—and Plan Propio de Investigación 2018—Programa Contratos-Puente (to GS-D); and Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidadesgrant SOMM17/6107/UGR (to JRR) via the ERDF., Background: Several studies have explored the role of human brown adipose tissue (BAT) in energy expenditure. However, the link between BAT and appetite regulation needs to be more rigorously examined. Objective: We aimed to investigate the associations of BAT volume and 18F-fluordeoxyglucose (18F-FDG) uptake after a personalized cold exposure with energy intake and appetite-related sensations in young healthy humans. Methods: A total of 102 young adults (65 women; age: 22.08 ± 2.17 y; BMI: 25.05 ± 4.93 kg/m 2) took part in this cross-sectional study. BAT volume, BAT 18F-FDG uptake, and skeletal muscle 18FFDG uptake were assessed by means of static 18F-FDG positronemission tomography and computed tomography scans after a 2-h personalized exposure to cold. Energy intake was estimated via an objectively measured ad libitum meal and three nonconsecutive 24-h dietary recalls. Appetite-related sensations (i.e., hunger and fullness) were recorded by visual analog scales before and after a standardized breakfast (energy content = 50% of basal metabolic rate) and the ad libitum meal. Body composition was assessed by a whole-body DXA scan. Results: BAT volume and 18F-FDG uptake were not associated with quantified ad libitum energy intake (all P > 0.088), nor with habitual energy intake estimated from the 24-h dietary recalls (all P > 0.683). Lean mass was positively associated with both the energy intake from the ad libitum meal (β: 17.612, R2 = 0.213; P < 0.001) and the habitual energy intake (β: 16.052, R2 = 0.123; P = 0.001). Neither the interaction BAT volume × time elapsed after meal consumption nor that of BAT 18F-FDG uptake × time elapsed after meal consumption had any significant influence on appetite-related sensations after breakfast or after meal consumption (all P > 0.3). Conclusions: Neither BAT volume, nor BAT 18F-FDG uptake after cold stimulation, are related to appetite regulation in young adults. These results suggest BAT plays no important role in the regulation of energy intake in humans. This trial was registered at clinicaltrials.gov as NCT02365129., Fondo de Investigación Sanitaria del Instituto de Salud Carlos III grant PI13/01393 (to JRR), Retos de la Sociedad grant DEP2016-79512-R (to JRR), Redes Temáticas de Investigación Cooperativa grant Red SAMID RD16/0022 (to AG), Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidadesgrant SOMM17/6107/UGR (to JRR) via the ERDF.

This cross-sectional study investigates the relationship between the shed form of the Klotho protein (S-Klotho) in plasma, and cardiometabolic risk in healthy, sedentary adults. The study subjects were 214 healthy, sedentary adults (~64% women). Data were collected during the baseline assessments of two randomized controlled trials: The FIT-AGEING study (n=74 [~50% women] middle-aged adults aged 40-65 years) and the ACTIBATE study (n=140 [~70% women] young adults aged 18-25 years). A sex-specific cardiometabolic risk score was calculated for each subject based on waist circumference, systolic and diastolic blood pressure, and plasma glucose, high-density lipoprotein cholesterol and triglycerides. A significant inverse relationship was detected between S-Klotho and the cardiometabolic risk score of both the middle-aged men and women (β=-0.658, R2=0.433, P0.5), nor for the young, healthy men and women when analysed separately (all P>0.1). In conclusion, in healthy, sedentary, middle-aged adults, but not in young, healthy, sedentary adults, higher plasma S-Klotho concentrations are associated with a lower cardiometabolic risk score.

Objectives Brown adipose tissue (BAT) is important in the maintenance of cardiometabolic health in rodents. Recent reports appear to suggest the same in humans, although if this is true remains elusive partly because of the methodological bias that affected previous research. This cross-sectional work reports the relationships of cold-induced BAT volume, activity (peak standardized uptake, SUVpeak), and mean radiodensity (an inverse proxy of the triacylglycerols content) with the cardiometabolic and inflammatory profile of 131 young adults, and how these relationships are influenced by sex and body weight. Design This is a cross-sectional study. Methods Subjects underwent personalized cold exposure for 2 h to activate BAT, followed by static 18F-fluorodeoxyglucose PET-CT scanning to determine BAT variables. Information on cardiometabolic risk (CMR) and inflammatory markers was gathered, and a CMR score and fatty liver index (FLI) were calculated. Results In men, BAT volume was positively related to homocysteine and liver damage markers concentrations (independently of BMI and seasonality) and the FLI (all P ≤ 0.05). In men, BAT mean radiodensity was negatively related to the glucose and insulin concentrations, alanine aminotransferase activity, insulin resistance, total cholesterol/HDL-C, LDL-C/HDL-C, the CMR score, and the FLI (all P ≤ 0.02). In women, it was only negatively related to the FLI (P < 0.001). These associations were driven by the results for the overweight and obese subjects. No relationship was seen between BAT and inflammatory markers (P > 0.05). Conclusions A larger BAT volume and a lower BAT mean radiodensity are related to a higher CMR, especially in young men, which may support that BAT acts as a compensatory organ in states of metabolic disruption.

New appetite-regulating antiobesity treatments such as semaglutide and agents under investigation such as tirzepatide show promise in achieving weight loss of 15% or more. Energy expenditure, fat oxidation, and lean mass preservation are important determinants of weight loss and weight-loss maintenance beyond appetite regulation. This review discusses prior failures in clinical development of weight-loss drugs targeting energy expenditure and explores novel strategies for targeting energy expenditure: mitochondrial proton leak, uncoupling, dynamics, and biogenesis; futile calcium and substrate cycling; leptin for weight maintenance; increased sympathetic nervous system activity; and browning of white fat. Relevant targets for preserving lean mass are also reviewed: growth hormone, activin type II receptor inhibition, and urocortin 2 and 3. We endorse moderate modulation of energy expenditure and preservation of lean mass in combination with efficient appetite reduction as a means of obtaining a significant, safe, and long-lasting weight loss. Furthermore, we suggest that the regulatory guidelines should be revisited to focus more on the quality of weight loss and its maintenance rather than the absolute weight loss. Commitment to this research focus both from a scientific and from a regulatory point of view could signal the beginning of the next era in obesity therapies.

This study was funded by the Spanish Ministry of Economy and Competitiveness via the Fondo de Investigacion Sanitaria del Instituto de Salud Carlos III (PI13/01393) and PTA 12264-I, and by Retos de la Sociedad (DEP2016-79512-R) and European Regional Development Fund, the Spanish Ministry of Education (FPU 13/03410, FPU 15/04059), the Fundacion Iberoamericana de Nutricion (FINUT), the Redes Tematicas de Investigaci on Cooperativa RETIC network (Red SAMID RD16/0022), the AstraZeneca HealthCare Foundation, The University of Granada's Plan Propio de Investigacion 2016 -Excellence actions: Unit of Excellence on Exercise and Health (UCEES), the Junta de Andalucia, Consejeria de Conocimiento, Investigacion y Universidades (ERDF, SOMM17/6107/UGR), and the Fundacion Alfonso Martin Escudero. This study is part of a PhD thesis conducted within the framework of the Biomedicine Doctoral Studies Programme of the University of Granada, Spain., Background: Harnessing cold-induced thermogenesis (CIT) and brown adipose tissue (BAT) activity has been proposed as a means of counteracting a positive energy balance, and thus of combating obesity and its related comorbidities. However, it has remained unclear whether CIT and BAT activity show diurnal variation in humans - knowledge that might allow treatments based on these factors to be timeoptimized. Methods: A randomized crossover experiment was designed to examine whether CIT shows morning/ evening variation in young, healthy adults (n ¼ 14, 5 women). On the first experimental day, subjects' shivering thresholds were determined following a cooling protocol. After z96 h had elapsed, the subjects then returned on two further days (approx. 48 h apart) at 08:00 h or 18:00 in random order. On both the latter days, the resting energy expenditure (REE) was measured before the subjects underwent personalized cold exposure (i.e., according to their shivering threshold). CIT was then assessed for 60 min by indirect calorimetry. In an independent cross-sectional study (n ¼ 133, 88 women), subjects came to the laboratory between 8:00 and 18:00 h and their BAT 18F-fluordeoxyglucose (18F-FDG) uptake was assessed after personalized cold stimulation. Results: Both the REE and CIT were similar in the morning and evening (all P > 0.05). Indeed, 60 min of personalized-mild cold exposure in the morning or evening elicited a similar change in energy expenditure (16.8 ± 12.8 vs. 15.7 ± 15.1% increase above REE, P ¼ 0.72). BAT 18F-FDG uptake was also similar in the morning, evening and afternoon (all P > 0.05). Conclusion: CIT does not appear to show morning/evening variation in young healthy adults, with the current study design and methodology. BAT 18F-FDG uptake appears not to change across the day either, although experiments with a within-subject study design are needed to confirm these findings., Spanish Ministry of Economy and Competitiveness via the Fondo de Investigacion Sanitaria del Instituto de Salud Carlos III PI13/01393 PTA 12264-I, Retos de la Sociedad DEP2016-79512-R, European Commission, Spanish Government FPU 13/03410 FPU 15/04059, Fundacion Iberoamericana de Nutricion (FINUT), Redes Tematicas de Investigaci on Cooperativa RETIC network Red SAMID RD16/0022, AstraZeneca, University of Granada's Plan Propio de Investigacion, Junta de Andalucia, Consejeria de Conocimiento, Investigacion y Universidades (ERDF) SOMM17/6107/UGR, Fundacion Alfonso Martin Escudero

Human brown adipose tissue (BAT) volume has been consistently claimed as inversely associated with whole-body adiposity. However, recent advances in the assessment of human BAT suggest that previously reported associations may have been biased. The present cross-sectional study investigates the association of BAT volume, mean radiodensity, and 18F-fluordeoxyglucose (18F-FDG) uptake (assessed via a static positron emission tomography-computerized tomography (PET-CT) scan after a 2-hour personalized cold exposure) with whole-body adiposity (measured by dual-energy X-ray absorptiometry) in 126 young adults (42 men/84 women; 25±5 kg/m2). BAT volume, but not 18F-FDG uptake, was positively associated with body mass index (BMI), fat mass, and visceral adipose tissue mass in men, but not in women. These associations were independent of the date when the PET-CT was performed, insulin sensitivity and body surface area. BAT mean radiodensity, an inverse proxy of BAT fat content, was negatively associated was with BMI, waist circumference, fat mass and visceral adipose tissue mas in men and with percentage fat mass in women. These results refute the widely held belief that human BAT volume is reduced in obese persons, at least in young adults, and suggest that it might even be the opposite in young men.

Context We examined whether obese individuals have a reduced maximal fat oxidation (MFO) and the intensity that elicit MFO (Fatmax) compared with normal weight and overweight persons, taking into account their level of cardiorespiratory fitness. Methods The study subjects were 138 sedentary adults (87 women) aged 30.1 ± 13.6 years. Based on their body mass index, subjects were categorized as being of normal weight (n = 66), overweight (n = 48), or obese (n = 24). MFO and Fatmax were determined for all subjects by indirect calorimetry, using a walking graded exercise test. MFO was expressed in absolute terms (g/min) and relative to whole-body lean mass (mg/kgleanmass/min). Cardiorespiratory fitness was assessed via a maximal treadmill test. Results No differences in absolute MFO and Fatmax values were seen between the obese, normal weight, and overweight subjects (all P > 0.2), although after adjusting for cardiorespiratory fitness, the obese subjects returned significantly higher values than did their normal weight and overweight counterparts (all P < 0.03). However, when expressed with respect to lean mass, the MFO of the normal weight subjects was significantly greater than that of the overweight and obese subjects, independent of age, sex, or cardiorespiratory fitness. Conclusions Obese individuals have higher absolute MFO values when cardiorespiratory fitness is taken into account, but when expressed with respect to lean mass, normal weight individuals show a greater capacity to oxidize fat during exercise per unit of metabolically active tissue independent of age, sex, or cardiorespiratory fitness. These findings suggest that obese individuals may suffer from metabolic inflexibility during exercise.

Objective: To investigate the efficacy of three different 8h time-restricted eating (TRE) schedules (i.e., early, late, and self-selected) over 4 weeks on body weight and waist/hip circumferences in adults with overweight/obesity from southern Spain. Methods: A total of 22 adults with a baseline eating window ≥12h (13 women; 48 ± 10 years old; BMI: 32.7 ± 5.8 kg/m2) were randomly assigned to early (first meal within the first 2h after waking up), late (first meal 5-7h after waking up) or a self-selected (selecting the 8h eating window each day) TRE groups. Results: Body weight change was -1.7 ± 2.1kg (P=0.078), -0.8 ± 2.2kg (P=0.386), and -1.0 ± 0.9kg (P=0.020) for the early, late, and self-selected TRE groups. Changes in body weight and waist/hip circumferences did not differ across TRE groups (all P≥0.197; Figure 1). Conclusions: These results suggest that early, late, and self-selected TRE produce similar changes in body weight and waist/hip circumferences over 4 weeks in adults with overweight/obesity. Future, bigger, and longer studies are needed to confirm these findings. Figure 1. Changes in body weight and waist/hip circumferences across early (dark), late (gray), and self-selected (light) TRE groups. F statistic, P values and partial eta squared are from ANCOVAs adjusting for baseline values. M, males; F, females Disclosure M. Dote montero: None. J. R. Ruiz: None. R. Sevilla-lorente: None. E. Merchan-ramirez: None. J. Nunez-lopez: None. S. Mochon-benguigui: None. F. Amaro-gahete: None. F. Acosta: None. G. Sanchez-delgado: None. I. Labayen: None. Funding Spanish Ministry of Universities (FPU18/03357)

Human brown adipose tissue (BAT) volume has been consistently claimed as inversely associated with whole-body adiposity. However, recent advances in the assessment of human BAT suggest that previously reported associations may have been biased. The present cross-sectional study investigates the association of BAT volume, mean radiodensity, and 18F-fluordeoxyglucose (18F-FDG) uptake (assessed via a static positron emission tomography-computerized tomography (PET-CT) scan after a 2-hour personalized cold exposure) with whole-body adiposity (measured by dual-energy X-ray absorptiometry) in 126 young adults (42 men / 84 women; 25±5 kg/m2). BAT volume, but not 18F-FDG uptake, was positively associated with body mass index (BMI), fat mass, and visceral adipose tissue mass in men, but not in women. These associations were independent of the date when the PET-CT was performed, insulin sensitivity and body surface area. BAT mean radiodensity, an inverse proxy of BAT fat content, was negatively associated was with BMI, waist circumference, fat mass and visceral adipose tissue mas in men and with percentage fat mass in women. These results refute the widely held belief that human BAT volume is reduced in obese persons, at least in young adults, and suggest that it might even be the opposite in young men.

Undercarboxylated osteocalcin (ucOC) could be a biomarker of glucose disturbances and cardiovascular risk. Our study aimed to determine the association between serum levels of ucOC and cardiovascular risk in metabolic syndrome (MetS) patients and to analyse its potential role as estimator of type 2 diabetes (T2D) risk in this population. This cross-sectional study included 235 patients with MetS, 53.2% women, aged 55–75 years. Circulating ucOC levels were measured by ELISA. Cardiovascular risk was determined as Z-score of the diagnostic criteria for MetS (CV-ZS). Linear regression model was performed to analyse the association between circulating ucOC and CV-ZS. A receiver operating curve (ROC) was performed to analyse the usefulness of ucOC as T2D risk estimator. Patients above the CV-ZS median showed signifcant lower ucOC levels. We found an inverse association between ucOC levels and CV-ZS in MetS patients without T2D. Patients with ucOC levels below the 25th percentile showed worse cardiometabolic profle and higher cardiovascular and T2D risk. The area under the curve performed better when ucOC levels were included along with the classic T2D risk factors. The measurement of circulating ucOC could be a useful tool to identify increased cardiovascular and T2D risk in MetS patients without T2D., Junta de Andalucia PI-0207-2016, European Union (EU) PI18-00803 PI18-01235

Heart rate variability (HRV) is a non-invasive indicator of autonomic nervous system function. HRV recordings show artefacts due to technical and/or biological issues. The Kubios software is one of the most used software to process HRV recordings, offering different levels of threshold-based artefact correction (i.e., Kubios filters). The aim of the study was to analyze the impact of different Kubios filters on the quantification of HRV derived parameters from short-term recordings in three independent human cohorts. A total of 312 participants were included: 107 children with overweight/obesity (10.0 &plusmn, 1.1 years, 58% men), 132 young adults (22.2 &plusmn, 2.2 years, 33% men) and 73 middle-aged adults (53.6 &plusmn, 5.2 years, 48% men). HRV was assessed using a heart rate monitor during 10&ndash, 15 min, and the Kubios software was used for HRV data processing using all the Kubios filters available (i.e., 6). Repeated-measures analysis of variance indicated significant differences in HRV derived parameters in the time-domain (all p &lt, 0.001) across the Kubios filters in all cohorts, moreover similar results were observed in the frequency-domain. When comparing two extreme Kubios filters, these statistical differences could be clinically relevant, e.g. more than 10 ms in the standard deviation of all normal R-R intervals (SDNN). In conclusion, the results of the present study suggest that the application of different Kubios filters had a significant impact on HRV derived parameters obtained from short-term recordings in both time and frequency-domains.

Objective This study aimed to describe the energy expenditure (EE) and macronutrient oxidation response to an individualized nonshivering cold exposure in young healthy adults. Methods Two different groups of 44 (study 1: 22.1 [SD 2.1] years old, 25.6 [SD 5.2] kg/m(2), 34% men) and 13 young healthy adults (study 2: 25.6 [SD 3.0] years old, 23.6 [SD 2.4] kg/m(2), 54% men) participated in this study. Resting metabolic rate (RMR) and macronutrient oxidation rates were measured by indirect calorimetry under fasting conditions in a warm environment (for 30 minutes) and in mild cold conditions (for 65 minutes, with the individual wearing a water-perfused cooling vest set at an individualized temperature adjusted to the individual's shivering threshold). Results In study 1, EE increased in the initial stage of cold exposure and remained stable for the whole cold exposure (P < 0.001). Mean cold-induced thermogenesis (9.56 +/- 7.9 kcal/h) was 13.9% +/- 11.6% of the RMR (range: -14.8% to 39.9% of the RMR). Carbohydrate oxidation decreased during the first 30 minutes of the cold exposure and later recovered up to the baseline values (P < 0.01) in parallel to opposite changes in fat oxidation (P < 0.01). Results were replicated in study 2. Conclusions A 1-hour mild cold exposure individually adjusted to elicit maximum nonshivering thermogenesis induces a very modest increase in EE and a shift of macronutrient oxidation that may underlie a shift in thermogenic tissue activity. This study was supported by the Spanish Ministry of Economy and Competitiveness via the Fondo de Investigacion Sanitaria del Instituto de Salud Carlos III (PI13/01393 and PTA 12264-I); the Retos de la Sociedad (DEP2016-79512-R) and European Regional Development Funds (ERDF); the Spanish Ministry of Education (FPU13/04365, FPU14/04172, and FPU15/04059); the Fundacion Iberoamericana de Nutricion; the Redes Tematicas de Investigacion Cooperativa (RETIC, red de Salud Materno Infantil y del Desarrollo 16/0022); the AstraZeneca HealthCare Foundation; the University of Granada Plan Propio de Investigación 2016 excellence actions (Unit of Excellence on Exercise and Health and Plan Propio de Investigacion 2018: Programa Contratos-Puente and Programa Perfeccionamiento de Doctores); the Junta de Andalucía, Consejeria de Conocimiento, Investigación y Universidades (ERDF; SOMM17/6107/UGR); and the Fundación Alfonso Maríin Escudero.

Regular physical activity (PA) is an important part of the treatment of several medical conditions, including overweight and obesity, in which there may be a weakened appetite control. Eating behaviour traits influence weight control and may be different in active and sedentary subjects. This paper reports the relationships between the time spent in sedentary behaviour and physical activity (PA) of different intensity, and eating behaviour traits in young, healthy adults. Additionally, it reports the results of a six-month-long, randomized, controlled trial to examine the effect of an exercise intervention on eating behaviour traits. A total of 139 young (22.06 &plusmn, 2.26 years) healthy adults (68.35% women) with a Body Mass Index (BMI) of 24.95 &plusmn, 4.57 kg/m2 were enrolled. Baseline assessments of habitual PA were made using wrist-worn triaxial accelerometers, eating behaviour traits were examined via the self-reported questionnaires: Binge Eating, Three-Factor Eating Questionnaire-R18 and Control of Eating Questionnaire. The subjects were then randomly assigned to one of three groups: control (usual lifestyle), moderate-intensity exercise (aerobic and resistance training 3&uml, C4 days/week at a heart rate equivalent to 60% of the heart rate reserve (HRres) for the aerobic component, and at 50% of the 1 repetition maximum (RM) for the resistance component), or vigorous-intensity exercise (the same training but at 80% HRres for half of the aerobic training, and 70% RM for the resistance training). At baseline, sedentary behaviour was inversely associated with binge eating (r = &minus, 0.181, p &lt, 0.05) and with uncontrolled eating (r = &minus, 0.286, p = 0.001). Moderate PA (MPA) was inversely associated with craving control (r = &minus, 0.188, p &lt, 0.05). Moderate-to-vigorous PA (MVPA) was directly associated with binge eating (r = 0.302, p &lt, 0.001) and uncontrolled eating (r = 0.346, p &lt, 0.001), and inversely associated with craving control (r = &minus, 0.170, p &lt, 0.015). Overall, PA was directly associated with binge eating (r = 0.275, p = 0.001), uncontrolled eating (r = 0.321, p &lt, 0.001) and emotional eating (r = 0.204, p &lt, 0.05). Additionally, only emotional eating was modified by the intervention, increasing in the vigorous-intensity exercise group (p &lt, 0.05). In summary, we observed that time spent in sedentary behaviour/PA of different intensity is associated with eating behaviour traits, especially binge eating in young adults. In contrast, the six-month exercise intervention did not lead to appreciable changes in eating behaviour traits.

Procedures: We measured 125 individuals after a personalized cooling protocol with a static [18F]FDG-PET/CT scan. We quantified BAT using different combination of threshold in every single HU for all participants. Results: We observed that the SUV threshold influences BAT quantification by [18F]FDG-PET/ CT scans more than the HU range. We found that the range from − 50 to − 10 HU had the highest proportion of total BAT volume (43.2 %), which represents 41.4 % of the total BAT metabolic activity in our cohort. We also observed that BAT volume was not different between categories of body mass index, as well as BAT activity (SUVmean). In addition, BAT was less dense in women than in men, although the BAT activity (SUVmean) was higher in all ranges of HU. We also observed that the radiodensity of BAT located in the cervical area was mainly in the range from − 50 to − 10 HU. Conclusion: Therefore, all future human studies using static [18F]FDG-PET/CT scans should include BAT in the radiodensity range from − 50 to − 10 HU., This study was supported by the Spanish Ministry of Economy and Competitiveness, Fondo de Investigación Sanitaria del Instituto de Salud Carlos III (PI13/01393) and Retos de la Sociedad (DEP2016-79512-R), Fondos Estructurales de la Unión Europea (FEDER), by the Spanish Ministry of Education (FPU 13/04365), by the Fundación Iberoamericana de Nutrición (FINUT), the Redes Temáticas de Investigación Cooperativa RETIC (Red SAMID RD16/0022), the AstraZeneca HealthCare Foundation, the University of Granada Plan Propio de Investigación 2016 - Excellence actions: Unit of Excellence on Exercise and Health (UCEES) - and Plan Propio de Investigación 2018 - Programa Contratos-Puente, and the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades (FEDER, ref. SOMM17/6107/UGR).

New findings What is the central question of this study? In some studies, biopsies have been performed of the subcutaneous adipose tissue in the abdomen, and they failed to find browning markers. Is the abdomen the right place to take biopsies? What is the main finding and its importance? For first time, we observed that the glucose uptake in the dorsocervical subcutaneous adipose tissue is higher in comparison to other areas of subcutaneous adipose tissue. Abstract Neonates have subcutaneous brown adipose tissue (BAT) in the dorsocervical area, and it is thought that these depots gradually disappear with age. Here, we determined that young adults have high 18 F-flurodeoxyglucose (18 F-FDG) uptake in the subcutaneous adipose tissue (SAT) of the dorsocervical area. A total of 133 young adults (age 22 ± 2 years; body mass index 25 ± 5 kg m2 ) were included in the study. We performed a shivering threshold test for every participant. Later, we performed 2 h of personalized cold exposure, immediately before a positron emission tomography/computed tomography scan. We showed that 23 of 133 participants had 18 F-FDG uptake in the dorsocervical area that achieved the criteria to be considered BAT, mainly in women (96%, n = 22 of 23). In the whole sample, the glucose uptake in the SAT of the dorsocervical area was positively correlated with BAT volume and activity located in the supraclavicular area. We showed that the 18 F-FDG uptake of the SAT of the dorsocervical area in humans is different from that of other SAT areas. Future studies are warranted to confirm the brown signature of this tissue.

Brown adipose tissue (BAT) activity is influenced by the outdoor temperature variation. However, people spend most of their time indoors, especially in colder regions and during cold seasons. Therefore, outdoor temperature is probably not an accurate tool to quantify the exposure of the participants before BAT quantification. We studied the association of wrist and personal environmental temperatures with cold-induced BAT and skeletal muscle [18F]fluorodeoxyglucose ([18F]FDG) uptake in adults. A total of 74 participants wore two iButtons during 7 days to measure wrist temperature (WT) and personal level of environmental temperature (Personal-ET). Thereafter, we performed a 2-h personalized cooling protocol before performing an [18F]FDG-PET/CT scan. WT was negatively associated with BAT volume ( R2 = 0.122; P = 0.002) and BAT activity [standardized uptake value (SUV)peak, R2 = 0.083; P = 0.012]. Moreover, Personal-ET was negatively associated with BAT volume ( R2 = 0.164; P < 0.001), BAT activity (SUVmean and SUVpeak, all R2 ≥ 0.167; P < 0.001), and skeletal muscle activity (SUVpeak, R2 = 0.122; P = 0.002). Interestingly, the time exposed to a certain Personal-ET (16–20°C) positively correlated only with [18F]FDG uptake by BAT (volume and activity; all P ≤ 0.05), whereas the time exposed to 12–15°C positively correlated only with measures of [18F]FDG uptake by skeletal muscle activity (all P ≤ 0.05). This study shows that WT and Personal-ET are associated with [18F]FDG uptake by BAT and skeletal muscle activity in adults within certain temperature thresholds. Moreover, our results suggest that [18F]FDG uptake by human BAT or skeletal muscle can be activated or inhibited in different ranges of ambient temperatures exposures. Results should be taken with caution because the observed associations were relatively weak.

Study Objectives Short sleep duration and sleep disturbances have been related to obesity and metabolic disruption. However, the behavioral and physiological mechanisms linking sleep and alterations in energy balance and metabolism are incompletely understood. In rodents, sleep regulation is closely related to appropriate brown adipose tissue (BAT) thermogenic activity, but whether the same is true in humans has remained unknown. The present work examines whether sleep duration and quality are related to BAT volume and activity (measured by 18F-FDG) and BAT radiodensity in humans. Methods A total of 118 healthy adults (69% women, 21.9 ± 2.2 years, body mass index: 24.9 ± 4.7 kg/m2) participated in this cross-sectional study. Sleep duration and other sleep variables were measured using a wrist-worn accelerometer for seven consecutive days for 24 hours per day. The Pittsburgh Sleep Quality Index was used to assess sleep quality. All participants then underwent a personalized cold exposure to determine their BAT volume, activity, and radiodensity (a proxy of the intracellular triglyceride content), using static positron emission tomography combined with computed tomography (PET/CI) scan. Results Neither sleep duration nor quality was associated with BAT volume or activity (the latter represented by the mean and peak standardized 18F-FDG uptake values) or radiodensity (all p > .1). The lack of association remained after adjusting the analyses for sex, date of PET/CT, and body composition. Conclusions Although experiments in rodent models indicate a strong relationship to exist between sleep regulation and BAT function, it seems that sleep duration and quality may not be directly related to the BAT variables examined in the present work. Clinical Trial Registration NCT02365129 (ClinicalTrials.gov).

Humans have metabolically active brown adipose tissue (BAT). However, what is the relation between exercise or physical activity with this tissue remains controversial. Therefore, the main aim of the present study is to examine whether cardiorespiratory fitness and muscular strength are associated with brown adipose tissue (BAT) volume and activity after exposure to cold in young, sedentary adults. Cardiorespiratory fitness was determined in 119 young, healthy, sedentary adults (68% women, age 21.9 ± 2.1 years, body mass index 25 ± 4.8 kg/m2) via the maximum treadmill exercise test, and their muscular strength assessed by the handgrip strength test and the 1-repetition maximum bench and leg press tests. Some days later, all subjects were exposed to 2 h of personalized exposure to cold and their cold-induced BAT volume and activity determined by a combination of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography and computed tomography scan. Cardiorespiratory fitness was associated with neither the BAT volume nor BAT activity (P ≥ 0.05). However, handgrip strength with respect to lean body mass was positively (though weakly) associated with BAT activity as represented by the 18F-FDG mean standardised uptake value (SUV) (β = 3.595, R2 = 0.039, P = 0.031) and SUVpeak value (β = 15.314, R2 = 0.037, P = 0.035). The above relationships remained after adjusting for several confounders. No other associations were found. Handgrip strength with respect to lean body mass is positively associated with BAT activity (SUVmean and SUVpeak) in young adults after exposure to cold - but only weakly. Further studies are needed to reveal the relationship between muscular fitness and human BAT characteristics., This study was supported by the Spanish Ministry of Economy and Competitiveness via the Fondo de Investigación Sanitaria del Instituto de Salud Carlos III (PI13/01393), Retos de la Sociedad (DEP2016-79512-R) and European Regional Development Funds (ERDF), the Spanish Ministry of Education (FPU13/04365 and FPU14/04172), the Fundación Iberoamericana de Nutrición (FINUT), the Redes Temáticas de Investigación Cooperativa RETIC (Red SAMID RD16/0022), the AstraZeneca HealthCare Foundation, the University of Granada Plan Propio de Investigación 2016 -Excellence actions: Unit of Excellence on Exercise and Health (UCEES) - and Plan Propio de Investigación 2018 - Programa Contratos-Puente, and the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades (ERDF: SOMM17/6107/UGR).

Humans have metabolically active brown adipose tissue (BAT). However, what is the relation between exercise or physical activity with this tissue remains controversial. Therefore, the main aim of the present study is to examine whether cardiorespiratory fitness and muscular strength are associated with brown adipose tissue (BAT) volume and activity after exposure to cold in young, sedentary adults. Cardiorespiratory fitness was determined in 119 young, healthy, sedentary adults (68% women, age 21.9 ± 2.1 years, body mass index 25 ± 4.8 kg/m2) via the maximum treadmill exercise test, and their muscular strength assessed by the handgrip strength test and the 1-repetition maximum bench and leg press tests. Some days later, all subjects were exposed to 2 h of personalized exposure to cold and their cold-induced BAT volume and activity determined by a combination of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography and computed tomography scan. Cardiorespiratory fitness was associated with neither the BAT volume nor BAT activity (P ≥ 0.05). However, handgrip strength with respect to lean body mass was positively (though weakly) associated with BAT activity as represented by the 18F-FDG mean standardised uptake value (SUV) (β = 3.595, R2 = 0.039, P = 0.031) and SUVpeak value (β = 15.314, R2 = 0.037, P = 0.035). The above relationships remained after adjusting for several confounders. No other associations were found. Handgrip strength with respect to lean body mass is positively associated with BAT activity (SUVmean and SUVpeak) in young adults after exposure to cold - but only weakly. Further studies are needed to reveal the relationship between muscular fitness and human BAT characteristics.

This study is part of a Ph.D. thesis conducted in the Biomedicine Doctoral Studies of the University of Granada, Spain., Currently, 18 [F]-Fluorodeoxyglucose (18F-FDG) in combination with a positron emission tomography/computed tomography (PET/CT) scan analysis is the most commonly used method to quantify human BAT volume and activity. However, this technique presents several drawbacks which negatively affect participant's health. The aim of the present work is to determine whether supraclavicular skin temperature can be used as an indirect marker of cold-induced BAT and skeletal muscle 18F-FDG uptake in adults, while taking into account body composition. We performed a personalized cooling protocol just before an 18F-FDG-PET/CT scan, and we measured supraclavicular skin temperature before (in warm conditions) and after the cooling protocol in 88 adults (n = 57 women, mean age: 21.9 ± 2.1 years old, body mass index: 24.5 ± 4.3 km/m2). We found that supraclavicular skin temperature at the warm and cold periods was weakly and positively associated with BAT activity (SUVmean and SUVpeak: β = 3.000; R2 = 0.072; P = 0.022 and β = 2.448; R2 = 0.060; P = 0.021), but not with skeletal muscle 18F-FDG uptake, after controlling for body composition. We performed further analyses and the positive associations persisted only in the group of women. In conclusion, supraclavicular skin temperature in warm and cold conditions seems to be related with cold-induced 18F-FDG uptake by BAT only in women, although the low explained variance of these associations means that there are other factors involved in the supraclavicular skin temperature., This study was supported by the Spanish Ministry of Economy and Competitiveness, Fondo de Investigación Sanitaria del Instituto de Salud Carlos III (PI13/01393) and Retos de la Sociedad (DEP2016-79512-R), Fondos Estructurales de la Unión Europea (FEDER), by the Spanish Ministry of Education (FPU 13/04365, 14/04172, and 16/05159), by the Fundación Iberoamericana de Nutrición (FINUT), by the Redes temáticas de investigación cooperativa RETIC (Red SAMID RD16/0022), by AstraZeneca HealthCare Foundation and by the University of Granada Plan Propio de Investigación 2016 -Excellence actions: Unit of Excellence on Exercise and Health (UCEES) - and Plan Propio de Investigación 2018 - Programa Contratos-Puente, and the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades (FEDER: ref. SOMM17/6107/UGR).

Human brown adipose tissue (BAT) has attracted clinical interest not only because it dissipates energy but also for its potential capacity to counteract obesity and related metabolic disorders (e.g., insulin resistance and dyslipidemia). Cold exposure is the most powerful stimulus for activating and recruiting BAT, and this stimulatory effect is mediated by the transient receptor potential (TRP) channels. BAT can also be activated by other receptors such as the G-protein-coupled bile acid receptor 1 (GPBAR1) or beta-adrenergic receptors. Interestingly, these receptors also interact with several dietary components; in particular, capsinoids and tea catechins appear to mimic the effects of cold through a TRP-BAT axis, and they consequently seem to decrease body fat and improve metabolic blood parameters. This systematic review critically addresses the evidence behind the available human studies analyzing the effect of several dietary components (e.g., capsinoids, tea catechins, and ephedrine) on BAT activity. Even though the results of these studies are consistent with the outcomes of preclinical models, the lack of robust study designs makes it impossible to confirm the BAT-activation capacity of the specified dietary components. Further investigation into the effects of dietary components on BAT is warranted to clarify to what extent these components could serve as a powerful strategy to treat obesity and related metabolic disorders.

Having valid and reliable resting energy expenditure (REE) estimations is crucial to establish reachable goals for dietary and exercise interventions. However, most of the REE predictive equations were developed some time ago and, as the body composition of the current population has changed, it is highly relevant to assess the validity of REE predictive equations in contemporary young adults. In addition, little is known about the role of sex and weight status on the validity of these predictive equations. Therefore, this study aimed to investigate the role of sex and weight status in congruent validity of REE predictive equations in young adults. A total of 132 young healthy adults (67.4% women, 18&ndash, 26 years old) participated in the study. We measured REE by indirect calorimetry strictly following the standard procedures, and we compared it to 45 predictive equations. The most accurate equations were the following: (i) the Schofield and the &ldquo, Food and Agriculture Organization of the United Nations/World Health Organization/United Nations&rdquo, (FAO/WHO/UNU) equations in normal weight men, (ii) the Mifflin and FAO/WHO/UNU equations in normal weight women, (iii) the Livingston and Korth equations in overweight men, (iv) the Johnstone and Frankenfield equations in overweight women, (v) the Owen and Bernstein equations in obese men, and (vi) the Owen equation in obese women. In conclusion, the results of this study show that the best equation to estimate REE depends on sex and weight status in young healthy adults.

We are grateful to Ms. Carmen Sainz-Quinn for assistance with the English language. We are grateful to Alberto Quesada-Aranda for helping with the development of the Temperatus software (Free trial in http://profth.ugr.es/temperatus)., This study is part of a Ph.D. Thesis conducted in the Biomedicine Doctoral Studies of the University of Granada, Spain., Brown adipose tissue (BAT) thermogenic activity is commonly assessed with a positron emission tomography with computed tomography scan (PET/CT). This technique has several limitations and alternative techniques are needed. Supraclavicular skin temperature measured with iButtons and infrared thermography (IRT) has been proposed as an indirect marker of BAT activity. We studied the concurrent validity of skin temperature measured with iButtons vs. IRT and the association of supraclavicular skin temperature measured with iButtons and IRT with BAT. We measured skin temperature upon a shivering threshold test with iButtons and IRT in 6 different regions in 12 participants (n = 2 men). On a separate day, we determined supraclavicular skin temperature with an iButton and IRT after 2 h of a personalized cooling protocol. Thereafter, we quantified BAT volume and activity by PET/CT. We observed that the absolute differences between the devices were statistically different from 0 (all P, This study was supported by the Spanish Ministry of Economy and Competitiveness via the Fondo de Investigación Sanitaria del Instituto de Salud Carlos III (PI13/01393), Retos de la Sociedad (DEP2016-79512-R), PTA 12264-I, and European Regional Development Fund (ERDF), the Spanish Ministry of Education (FPU 13/04365, FPU14/04172, FPU15/05337, and FPU15/04059), by the Spanish Ministry of Science and Innovation-MINECO (RYC-2014-16938), the Fundación Iberoamericana de Nutrición (FINUT), the Redes Temáticas de Investigación Cooperativa RETIC (Red SAMID RD16/0022), the AstraZeneca HealthCare Foundation, the University of Granada Plan Propio de Investigación 2016 -Excellence actions: Unit of Excellence on Exercise and Health (UCEES) - and Plan Propio de Investigación 2018 - Programa Contratos-Puente, and the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades (ERDF, ref. SOMM17/6107/UGR). This study is part of a Ph.D.

The authors would like to thank all the participants who took part in this investigation. This study is part of a PhD thesis conducted in the Biomedicine Doctoral Studies of the University of Granada, Spain. We are grateful to Alberto Quesada-Aranda for helping with the development of the Temperatus software (free trial at http://profith.ugr.es/ temperatus?lang=en). We are grateful to Ms Carmen Sainz-Quinn for assistance with English-language editing, Objective: This study aimed to examine whether brown adipose tissue (BAT) or skeletal muscle activity mediates the relationship between personal level of environmental temperature (Personal-ET) and wrist skin temperature (WT). Moreover, we examined whether BAT and skeletal muscle have a mediating role between Personal-ET and WT (as a proxy of peripheral vasoconstriction/vasodilation). Methods: The levels of BAT were quantified by cold-induced 18F-fluorodeoxyglucose–positron emission tomography/computed tomography scan and measured the Personal-ET and WT by using iButtons (Maxim Integrated, Dallas, Texas) in 75 participants (74.6% women). Results: The study found that BAT volume and metabolic activity played a positive and significant role (up to 25.4%) in the association between Personal-ET and WT. In addition, at the coldest temperatures, the participants with lower levels of WT (inducing higher peripheral vasoconstriction) had higher levels of BAT outcomes, whereas in warm temperatures, participants with higher levels of WT (inducing higher peripheral vasodilation) had lower levels of BAT outcomes. The study did not find any mediating role of skeletal muscle activity. Conclusions: BAT volume and metabolic activity play a role in the relationship between Personal-ET and WT. Moreover, the data suggest that there are two distinct phenotypes: individuals who respond better to the cold, both through nonshivering thermogenesis and peripheral vasoconstriction, and individuals who respond better to the heat., This study was supported by the Spanish Ministry of Economy and Competitiveness, Fondo de Investigación Sanitaria del Instituto de Salud Carlos III (PI13/01393), Retos de la Sociedad (DEP2016‐79512‐R), and Fondos Estructurales de la Unión Europea (FEDER); by the Spanish Ministry of Education (FPU 13/04365); by the Fundación Iberoamericana de Nutrición; by the Redes Temáticas de Investigación Cooperativa RETIC (Red SAMID RD16/0022); by AstraZeneca HealthCare Foundation; by the University of Granada, Plan Propio de Investigación 2016, Excellence actions: Units of Excellence; Unit of Excellence on Exercise and Health (UCEES); and by the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades and European Regional Development Fund (ERDF), ref. SOMM17/6107/UGR, Programa Contratos‐Puente. MAR is supported by a predoctoral research grant from University Jaume I (PREDOC/2015/13). AMN was supported by the Ministry of Economy and Competitiveness, the Instituto de Salud Carlos III through the Centro de Investigación Biomédica en Red Fragilidad y Envejecimiento Saludable (CB16/10/00239), and grant 19899/GERM/15 (cofinanced by FEDER).

Dairy products are thought to improve recovery after both resistance and endurance exercises due to their nutritional proprieties. We systematically reviewed the effects of dairy product intake on exercise performance and recovery of muscle function in humans. A literature search was conducted in the MEDLINE (via PubMed) and Web of Science databases from their inception to 15th April 2018. The initial search retrieved 7708 articles, and a total of 11 studies were finally included after applying inclusion and exclusion criteria. All the selected studies were conducted with cow’s milk. Whereas some studies found significant positive effect of cow’s milk on exercise performance and recovery of muscle function, others did not find any effect. These controversies could be due to the heterogeneity of cow’s milk ingestion (e.g., amount of cow’s milk, timing of consuming the cow’s milk), to the type of intervention, and to the large heterogeneity of outcomes measured. Limited studies exist examining the effects of cow’s milk consumption and its influence on exercise performance and recovery of muscle function, therefore further studies are needed to draw more definitive conclusions., The study was supported by the Spanish Ministry of Education (FPU 13/ 04365 and 15/04059), by the Redes temáticas de investigación cooperativa RETIC (Red SAMID RD16/0022), and by the University of Granada Plan Propio de Investigación 2016 -Excellence actions: Unit of Excellence on Exercise and Health (UCEES) - and Plan Propio de Investigación 2018 - Programa Contratos-Puente, and the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades (ERDF: ref. SOMM17/6107/UGR), and by the Interprofessional Dairy Organization (INLAC) of Spain.

The time spent in sedentary behaviour represents an important public health burden. To reduce sedentary time in the general population, the simplest, most effective, and most accessible method is to decrease lying and sitting time. We aimed to compare differences on energy expenditure (EE) across lying, sitting, and standing positions; and to analyse the associations between the change on EE of changing from one position to another and anthropometric and body composition parameters in young healthy adults. A total of 55 (69% women) young healthy adults aged 21.7 ± 2.2 participated in the study. We measured EE by indirect calorimetry across lying, sitting, and standing positions following the standard procedures. The EE was significantly higher in standing than in both lying and sitting positions (mean difference: 0.121±0.292 and 0.125±0.241 kcal/min, respectively; all P0.321). Our findings support the fact that increasing the time spent standing could be a simple strategy to slightly increase EE. Therefore, our results have important clinical implications including a better monitoring, characterizing, and promoting countermeasures to sedentariness through low-level physical activities., This work was supported by: JRR: Spanish Ministry of Economy and Competitiveness, Fondo de Investigacio´n Sanitaria del Instituto de Salud Carlos III (PI13/01393) and Retos de la Sociedad (DEP2016-79512-R); JRR: Fondos Estructurales de la Unio´n Europea (FEDER); FAG, GSD, JMA: Spanish Ministry of Education (FPU 13/04365, FPU14/04172, and FPU15/04059); JRR: Fundacio´n Iberoamericana de Nutricio´n (FINUT); JRR: Redes tema´ticas de investigacio´n cooperativa RETIC (Red SAMID RD16/0022); JRR: AstraZeneca HealthCare Foundation; JRR: University of Granada, Plan Propio de Investigacio´n 2016, Excellence actions: Units of Excellence, Unit of Excellence on Exercise and Health (UCEES)

OBJECTIVES: To investigate the feasibility and acceptability of three different 8h time-restricted eating (TRE) schedules (i.e., early TRE, late TRE, and self-selected TRE) over 4 weeks in adults with overweight/obesity from southern Spain. METHODS: A total of 22 adults with overweight/obesity and a baseline eating window ≥12h (13 women; 48 ± 10 years old; body mass index: 32.7 ± 5.8 kg/m(2)) were randomly assigned to one of the three 8h-TRE schedules: early TRE (first meal within the first 2h after waking up), late TRE (first meal 5–7h after waking up), and self-selected TRE (self-selected eating window). Feasibility and acceptability were assessed by adherence to the intervention, adverse events and validated questionnaires to assess sleep quality, depression, and anxiety. RESULTS: All participants completed the intervention. Adherence remained ≥95% in the late and self-selected TRE groups during the intervention, whereas it decreased from 94% (first week) to 68% (fourth week) in the early TRE group. Total adherence was not associated with baseline eating window (P = 0.644). The mean intervention eating window was 7.9 ± 0.5h, 7.1 ± 0.5h, and 7.4 ± 0.5h for the early, late, and self-selected TRE, respectively. Differences were noted between early and late TRE groups (P = 0.019). No serious adverse events were reported and no differences were observed in headache, nausea, acidity, diarrhea, thirstiness, hunger, cravings, tiredness, stress, irritability, and anxiety eating among TRE groups. After the intervention, the early TRE improved depression using two different validated questionnaires (P = 0.007 and P = 0.018), although no differences were observed across TRE groups (P = 0.863 and P = 0.197). A trend to significant improvement in sleep quality (P = 0.067) was observed in the early TRE group after the intervention, albeit no differences were noticed across TRE groups (P = 0.277). CONCLUSIONS: These results suggest that early TRE may have lower feasibility and acceptability than late and self-selected TRE in adults with overweight/obesity from southern Spain. However, early TRE appears to enhance depression and sleep quality. Lastly, no serious adverse events were noted; hence, TRE seems a safe nutrition. FUNDING SOURCES: N/A.

Background: Due to a clinical and public health interest of neck circumference (NC), a better understanding of this simple anthropometric measurement, as a valid marker of body composition is necessary. Methods: A total of 119 young healthy adults participated in this study. NC was measured over the thyroid cartilage and perpendicular to the longitudinal axis of the neck. Body weight, height, waist circumference (WC), and hip circumference were measured. A Dual X-ray absorptiometry (DXA) scan was used to determine fat mass, lean mass, and visceral adipose tissue (VAT). Additionally, body mass index (BMI) and triponderal mass index (TMI), the waist to hip and waist to height ratios, and the fat mass and lean mass indexes (FMI and LMI, respectively) were calculated. Results: NC was positively associated in women (W) and men (M), with BMI (rW = 0.70 and rM = 0.84, respectively), TMI (rW = 0.63 and rM = 0.80, respectively), WC (rW = 0.75 and rM = 0.86, respectively), VAT (rW = 0.74 and rM = 0.82, respectively), Waist/hip (rW = 0.51 and rM = 0.67, respectively), Waist/height (rW = 0.68 and rM = 0.83, respectively) and FMI (rW = 0.61 and rM = 0.81, respectively). The association between NC and indicators of body composition was however weaker than that observed by BMI, TMI, WC and Waist/height in both women and men. It is of note that in women, NC was associated with FMI, VAT and LMI independently of BMI. In men, adding NC to anthropometric variables did not improve the prediction of body composition, while slight improvements were observed in women. Conclusions: Taken together, the present study provides no indication for NC as a useful proxy of body composition parameters in young adults, yet future studies should explore its usefulness as a measure to use in combination with BMI, especially in women., This study was supported by the Spanish Ministry of Economy and Competitiveness Grants (DEP2016-79512-R and PTA 12264-I), Fondo de Investigación Sanitaria del Instituto de Salud Carlos III (PI13/01393), and Retos de la Sociedad (DEP2016-79512-R), Fondos Estructurales de la Unión Europea (FEDER), by the Spanish Ministry of Education (FPU 13/04365), by the Fundación Iberoamericana de Nutrición (FINUT), by the Redes temáticas de investigación cooperativa RETIC (Red SAMID RD16/0022), by AstraZeneca HealthCare Foundation and by the University of Granada, Plan Propio de Investigación 2016, Excellence actions: Units of Excellence; Scientific Unit of Excellence on Exercise and Health (UCEES), Plan Propio de Investigación 2018: Programa Contratos-Puente and Programa Perfeccionamiento de Doctores, by the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades, the European Regional Development Funds (ref. SOMM17/6107/UGR), by the Fundación Alfonso Martín Escudero, and by the Fundación Carolina (C.2016-574961). This study is part of a Ph.D. Thesis conducted in the Biomedicine Doctoral Studies of the University of Granada, Spain.

The method used to select representative gas exchange data from large datasets influences the resting metabolic rate (RMR) returned. This study determines which of three methods yields the lowest RMR (as recommended for use in human energy balance studies), and in which method the greatest variance in RMR is explained by classical determinants of this variable. A total of 107 young and 74 middle-aged adults underwent a 30 min RMR examination using a breath-by-breath metabolic cart. Three gas exchange data selection methods were used: (i) steady state (SSt) for 3, 4, 5, or 10 min, (ii) a pre-defined time interval (TI), i.e., 6&ndash, 10, 11&ndash, 15, 16&ndash, 20, 21&ndash, 25, 26&ndash, 30, 6&ndash, 25, or 6&ndash, 30 min, and (iii) &ldquo, filtering&rdquo, setting thresholds depending on the mean RMR value obtained. In both cohorts, the RMRs yielded by the SSt and filtering methods were significantly lower (p &lt, 0.021) than those yielded by the TI method. No differences in RMR were seen under the different conditions of the SSt method, or of the filtering method. No differences were seen between the methods in terms of the variance in RMR explained by its classical determinants. In conclusion, the SSt and filtering methods return the lowest RMRs and intra-measurement coefficients of variation when using breath-by-breath metabolic carts.