Search

Although extensive studies have focused on carbon and water balance from aboveground measurements, the link between the belowground and aboveground processes deserves greater attention. In this context, the aim of this work was to assess the bi-directional feedback between whole-plant respiration and transpiration. The study was performed on 25 saplings of Sugi (Japanese cedar, Cryptomeria japonica D. Don), including dominant and suppressed individuals (total fresh weight ranging between 0.2 and 8.0 kg). During one week, the integrated water use (WU) was determined using the Deuterium dilution method. After this, the trees were uprooted and the root, stem, and leaf respiration were measured using incubation chambers and CO2 infrared sensors. The stem and root respiration followed a power response to mass (power exponent b &lt, 1), implying a decline in mass-specific respiration with size. Conversely, the leaf respiration followed a near-linear increase with size (power exponent b &asymp, 1), but was negatively affected by the stem density, indicating the hydraulic limitations of the leaf metabolism. The water use followed a power response with the tree size (b &lt, 1), showing a decline in the transpiration per leaf mass with the tree size, but was also negatively correlated with the stem density. Our results indicate that dominant trees are more efficient in the use of water, and highlight the role of hydraulic limitations to leaf metabolism in suppressed trees.

There is no data on the prevalence of overweight and obesity in young Syrian boys. Therefore, the present study aimed to provide baseline and reference data on the prevalence of overweight and obesity among young Syrian boys using skin-fold thickness measurements and deuterium dilution (DD) as a reference method. The sample of 2470 healthy Syrian 18- to 19-year-old boys were enrolled in this study. SFTs were measured at the biceps (B), triceps (T), subscapular (SI) and suprailiac locations (SS) were done and validated using the DD technique as a reference method. Receiver operating characteristics (ROC) curve was drawn to determine appropriate cut-off points of the Σ2 limb SFT (T+B), Σ2 trunk SFT (SI+SS), Σ4 SFT (T+B+SI+SS) and Log Σ4 SFT for defining overweight and obesity. The overall prevalence of overweight and obesity in young Syrian boys, based on biceps SFT, triceps SFT, subscapular SFT, suprailiac SFT, Σ2 limb SFT, Σ2 trunk SFT, Σ4 SFT, logarithm Σ4 SFT, and DDT were 35.3%, 32%, 31.6%, 14.8%, 32.9%, 26.6%, 28.1%, 24.1%, 46.5%, respectively. Strongly positive correlation was found between SFT and total body fat in adolescents. For diagnosing overweight on the basis of Σ2 limb SFT, Σ2 trunk SFT, Σ4 SFT and logarithm Σ4 SFT, we propose the following cut-off points: 17.25 mm, 23.50 mm, 39.25 mm and 1.60, respectively. To predict obesity, Σ2 limb SFT, Σ2 trunk SFT, Σ4 SFT and logarithm Σ4 SFT threshold were increased to 23.25 mm, 32.50 mm, 55.25 and 1.75, respectively. Basing on SFT clearly leads to underestimates of the prevalence of weight problems among young boys. SFT measurement screen missed 11.2 to 31.7% of overall overweight and obesity cases.

Objective: Firstly, to compare food, and macronutrient intake as obtained from a single 24-h recall and a frequency questionnaire (FQ) covering a 14-day period in breast-fed infants aged 4 months of age. Secondly, nonbreast milk water intake (NB-WI, ml/day) was used as an estimation of energy and macronutrient intake, and NB-WI as calculated from FQ (NB-WIFQ) was compared with NB-WI as measured using the dose-to-the-mother (H2O)-H-2 turnover method (NB-WIDO) covering the same 14-day period.Design: Cross-sectional.Setting: Community-based study in urban Pelotas, Southern Brazil.Subjects: In all, 67 breast-fed infants aged 4 months of age recruited at birth.Main outcome measures: ( 1) Bias in estimations of food and macronutrient intake of the 24-h recall relative to FQ; ( 2) Bias in NB-WIFQ relative to NB-WIDO.Results: In infants with an energy intake(FQ) from complementary foods above the 50th percentile (1.03 kcal/day), estimations of water, tea, juice, and milk intake were not different between 24-h recall and FQ ( n = 34). Nor were estimations of energy and macronutrient intake ( protein, fat, and carbohydrates) different between the two methods, and bias was nonsignificant. NB-WIDO was divided into quintiles and compared with NB-WIFQ. The first two quintiles included negative values for NB-WIDO as a result of random errors of the (H2O)-H-2 turnover method. Subsequently, bias of NB-WIFQ relative to NB-WIDO was positive in the 1st ( P = 0.001) and 2nd quintile ( P = 0.638), respectively. Bias was negative for the three highest quintiles, and within this group, underestimation by FQ was significant for the 3rd and 4th quintile ( - 57.4%, P = 0.019; - 43.7%, P = 0.019).Conclusions: Firstly, at the age of 4 months FQ covering a 14-day period provides similar results on food and macronutrient intake as compared to a single 24-h recall for estimations of complementary liquid foods. Secondly, NB-WIFQ appeared to be a good proxy for macronutrient and energy intake in breast-fed infants receiving other liquids. In infants with NB-WIDO>0, the method provides a useful tool for the detection of bias from FQ, and results indicate an underestimation from FQ relative to the (H2O)-H-2 turnover method. This exercise could be applied wherever the (H2O)-H-2 turnover method is used in combination with conventional food consumption techniques for measuring intake of nonbreast milk liquids of breast-fed infants in whom solid foods have not yet been introduced. It would help interpreting estimations of macronutrient intake, and could be relevant to studies of dietary intake of infants and its relationship with growth and health.Sponsorship: International Atomic Energy Agency through RC 10981/R1.

VAN MARKEN LICHTENBELT, W. D., F. HARTGENS, N. B. J. VOLLAARD, S. EBBING, and H. KUIPERS. Body Composition Changes in Bodybuilders: A Method Comparison. Med. Sci. Sports Exerc., Vol. 36, No. 3, pp. 490 – 497, 2004. Introduction: Few studies report on validation of body composition changes using the four-compartment model (4C), and no such studies are available in strength training. Here we present such a validation study for the determination of body fat and fat-free mass changes in bodybuilders, who used exercise and androgenic-anabolic steroids. Methods: The study was carried out with 27 male bodybuilders in a crosssectional study. Fifteen of these subjects also participated in an intervention program where body composition changes were measured. The 4C model served as the gold standard. The alternative mechanistic methods were underwater weighing (uww), deuterium dilution (dil), three-compartment model incorporating total body water (3Cw), three-compartment model incorporating bone mineral content (3Cb), and descriptive methods, namely dual-energy x-ray absorptiometry (DXA), prediction equations based on body mass index (BMI), skinfold measurement, and bioimpedance analyses. Results: From the cross-sectional study, it appeared that biases and errors of most mechanistic methods were small (maximal 0.5% BF and 3.4%BF, respectively; exception 3Cb model). The 3Cw model had the lowest error (0.9%BF). The descriptive methods had small biases (exception BMI) but relatively large errors (range: 5.5– 8%). Results on body composition changes (intervention study) were comparable with the results from the cross-sectional study. Conclusions: Using the 4C model as the standard for determination of body fat and fat-free mass, this study revealed that apart from the prediction equation based on BMI and the 3Cb model, all methods gave acceptable group mean values. When accurate measurements on body composition and/or body composition changes on an individual level are needed, only the 3Cw model could serve as an alternative for the 4C method. Key Words: ANDROGENIC-ANABOLIC STEROIDS, STRENGTH TRAINING, FOUR COMPARTMENT MODEL, DEUTERIUM DILUTION, DXA

BACKGROUND: In developing countries where access to water and food is not guaranteed, women may have to travel long distances or engage in intense physical activities to gather food. This may compromise their water requirements and overall nutritional status. The aim of the study was to determine water turnover, physical activity and body composition among women in Kenya and to describe the differences between rural and urban Kenyan women. METHODS: Thirty women from Narok County who were not pregnant at the time of the study were recruited. Body mass index (BMI) was calculated by dividing weight in kilograms by height in meters squared. Deuterium dilution was used to determine total body water (TBW) and water turnover was measured from deuterium elimination. Fat-free mass (FFM) was calculated by assuming a constant hydration fraction of 73.2%. Accelerometers (Actigraph GT3X) were used to assess physical activity and expressed as Vector magnitude counts per day (VM/day). Simple and multiple linear regressions were used to define the determinants of water turnover. RESULTS: Mean BMI was 23.4 +/- 4.1 and 21.5 +/- 3.8 among rural and urban women respectively. The prevalence of overweight (BMI > 25 kg/m(2)) was 24.1% and of underweight (BMI < 18.4 kg/m2)) was 25%. The mean total body water (TBW) was 29.3 +/- 4.2 liters (L) and water turnover was 3.2 +/- 0.8 liters per day (L/day). Water loss was positively associated with BMI (R(2) = .45, p < 0.001, n = 28) and Fat mass index (FMI) (R(2) = .41, p < 0.001, n = 28). Water loss was also positively associated with physical activity (PA) (R(2) = .25, p < 0.05, n = 22). Multiple regression analysis showed that physical activity in addition to BMI in the model explained an additional 15% of the variation in water turnover (r(2) = 0.53, p < 0.05; r(2) = 0.15, p < 0.05, n = 22) compared to BMI alone (r(2) = 0.38, p < 0.005 n = 22). CONCLUSION: BMI together with physical activity were the strongest predictors of water loss.

This study reports total body hydration and water distribution between the extracellular water (ECW) and the intracellular water (ICW) of a group of 15 elite male athletes compared with a group of 15 male subjects practising the same sport at 'amateur' level. Total body water (TBW) and ECW were assessed by means of deuterium and bromide dilution techniques respectively. Both TBW and body hydration were significantly higher in elite athletes than in non-competitive subjects (52.3 +/- 5.0 vs 46.1 +/- 4.2 litres p0.001 and 63.2 +/- 1.9 vs 60.2 +/- 1.9% body weight, p0.003 respectively). Likewise, both ECW the ratio of ECW to TBW were significantly higher in athletes than in control subjects (20.7 +/- 2.9 vs 16.1 +/- 1.8 litres, p0.0001 and 0.40 +/- 0.06 vs 0.35 +/- 0.03, p0.005 respectively). ICW was similar in both groups but the ICW to ECW ratio was significantly higher in the athletes compared to the recreational sportsmen (0.67 +/- 0.16 vs 0.54 +/- 0.07, p0.01). These data suggest that assumptions regarding the chemical composition of the standard human body may not be valid in elite athletes.

Body composition of 24 rural Beninese women was assessed in a pre- and a postharvest season by using skinfold-thickness measurements, bioelectrical-impedance analysis (BIA), and deuterium oxide (D2O) dilution. Fat mass assessed by D2O dilution was 12.3 +/- 3.3 kg; by skinfold-thickness measurements, 13.8 +/- 3.3 kg; and by BIA, 14.1 +/- 2.9 kg. Fat mass assessed by D2O was significantly lower (P less than 0.05) than fat mass assessed by the other two methods. Body weight in the postharvest season was 0.8 +/- 1.6 kg higher (P less than 0.05) than during the preharvest season. All three methods demonstrated that there were no significant changes in fat mass but that fat-free mass increased significantly (P less than 0.05) from pre- to postharvest season.

Objective: To validate the Tanita BC-418MA Segmental Body Composition Analyser and four-site skinfold measurements for the prediction of total body water (TBW), percentage fat-free mass (% FFM) and percentage body fat (%BF) in a population of rural Gambian children. Subjects/Methods: One hundred and thirty-three healthy Gambian children (65 males and 68 females). FFM estimated by the inbuilt equations supplied with the Tanita system was assessed by comparison with deuterium oxide dilution and novel prediction equations were produced. Deuterium oxide dilution was also used to develop equations for %BF based on four-site skinfolds (biceps, triceps, subscapular and suprailiac). Results: The inbuilt equations underestimated FFM compared to deuterium oxide dilution in all the sex and age categories (P

INTRODUCTION: The use of androgenic-anabolic steroids (AAS) among bodybuilders to increase muscle mass is widespread. Nandrolone decanoate (ND) is one of the most popular misused AAS, although the effects on body composition are equivocal. Therefore, the purpose of this study was to determine the effect of ND on body composition in male bodybuilders, with special reference to muscle mass alterations. METHODS: Using a randomized "double-blind" "placebo-controlled" design, 16 experienced male bodybuilders (age: 19-44 yr) either received ND (200 mg.wk(-1), intramuscularly) or placebo for 8 wk. Body composition was assessed using the four-component model, combining results from underwater weighing, dual-energy x-ray absorptiometry (DXA), and deuterium dilution. Total bone mineral content and density were measured using DXA. Water compartments (extracellular water [ECW] and intracellular water [ICW]) were determined using deuterium dilution and bromide dilution. RESULTS: ND administration resulted in significant increments of body mass (+2.2 kg), fat-free mass (FFM: +2.6 kg), and total body water (+1.4 kg). No significant changes in fat mass, percentage fat, ECW, ICW, ECW/ICW ratio, hydration of the FFM, and on bone mineral measurements were observed. CONCLUSIONS: The results show that the administration of 200 mg.wk(-1) of ND (intramuscularly) for 8 wk significantly increased body mass and FFM, whereas fat mass, bone mineral content, bone mineral density, and the hydration of the FFM remained unaffected. These data indicate that the changes can be attributed to an increase of muscle mass.

OBJECTIVE: To validate the assessment of total body water (TBW) and extracellular water (ECW) by multi-frequency bioelectrical impedance. SUBJECTS: Twenty-five overweight but otherwise healthy subjects and 20 lean subjects. DESIGN: Cross-sectional. MEASUREMENTS: TBW and ECW were determined by dilution techniques. Prediction equations from the literature were used to calculate TBW and ECW from measured impedance at 100 and 50 kHz or 1 and 5 kHz, respectively. In 18 of the obese subjects, impedance was also measured with the electrodes placed at proximal sites. RESULTS: In lean and obese subjects, significant correlations were observed between the impedance index (H2/Z) at high frequencies with TBW (r=0.90, P