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Background: Aging is associated with physical inactivity, low energy intake, and loss of skeletal muscle mass. It is not clear whether regular physical activity and adequate dietary protein intake can attenuate the loss of skeletal muscle mass. Objective: We hypothesized that the maintenance of physical activity and dietary protein intake would attenuate the age-related decline in total appendicular skeletal muscle mass. Design: Total appendicular skeletal muscle mass was determined by dual-energy X-ray absorptiometry in 44 healthy, older white men aged 49-85 y. Physical activity level was determined by using a uniaxial accelerometer over a 9-d period. Dietary protein intake was estimated from a 3-d food record. Results: Aging was inversely associated with total appendicular skeletal muscle mass in older men (r = -0.43; slope: -0.119 +/= 0.039 kg/y; P < 0.01). An effect of age on appendicular skeletal muscle mass persisted after standing height and physical activity were controlled for (r = -0.34; slope: -0.120 +/= 0.052 kg/y; P = 0.03). Furthermore, an effect of age on appendicular skeletal muscle mass persisted after standing height and dietary protein intake per kilogram body mass was controlled for (r = -0.41; slope: -0.127 +/= 0.045 kg/y; P < 0.01). Conclusions: Maintaining regular physical activity and adequate protein intake may not offset the age-related loss of appendicular skeletal muscle mass in older men. Prospective studies are needed to confirm these results and to determine whether anabolic physical activity (eg, strength training) can attenuate the age-related loss of muscle mass in the elderly. Copyright 1999 American Society for Clinical Nutrition [ABSTRACT FROM AUTHOR]

Multiple indices to assess insulin sensitivity calculated from mathematical equations based on fasting blood parameters or oral glucose tolerance data have been developed. Although these indices have frequently been validated using euglycemic-hyperinsulinemic clamp data, the utility of each equation in measuring change in insulin sensitivity over time remains uncertain. We examined change in insulin sensitivity in response to a 12-week diet and exercise intervention in 31 older men and women with impaired glucose tolerance using a euglycemic-hyperinsulinemic clamp and 10 commonly used insulin sensitivity equations. Mean glucose disposal as calculated from clamp data was significantly higher after the intervention compared with baseline (5.92 +/- 0.38 vs 5.18 +/- 0.30 mg . kg fat free mass(-1) . min(-1), P = .013). In contrast, none of the examined indices indicated a significant change in insulin sensitivity over time (all P > .3). A limits of agreement approach to compare insulin sensitivity calculated from each equation with the measure of glucose disposal from the clamp indicated overall imperfect agreement between measures (agreement limits ranged from +/-2.48 to +/-4.23 mg . kg fat free mass(-1) . min(-1)) despite significant bivariate correlations between indices and clamp data. The wide variability in the 95% prediction limits of agreement among equations suggests that these equations vary substantially from a euglycemic-hyperinsulinemic clamp in their ability to assess insulin sensitivity. Despite the observed limited agreement using this statistical approach, changes in several calculated indices were significantly correlated with changes in clamp data, suggesting that these indices may have some utility in tracking improvements in insulin sensitivity. Further research is necessary to examine agreement between indices and clamp data in larger, more heterogeneous populations and in response to other interventions where the magnitude of change in insulin sensitivity may be larger.

Purpose: Although data suggest that physical activity is associated with decreased insulin resistance, recommendations for exercise training are not specific for age or level of obesity. Therefore, we examined the influence of moderate-intensity (50% of VO2max) exercise training (MI) versus high-intensity (75% of VO2max) exercise training (HI) on insulin-stimulated glucose disposal (ISGD) in elderly individuals., Methods: Following medical examinations, 21 overweight (body mass index = 29 +/- 1 kg x m(-2)) elderly (74 +/- 1 yr) subjects were randomized to 1) HI, 2) MI, or a 3) nonexercising control group. Subjects enrolled in HI or MI completed a 12-wk exercise training regimen designed to expend 1000 kcal x wk. ISGD was assessed using a hyperinsulinemic, euglycemic clamp pre- and postintervention. ISGD was corrected for hepatic glucose production (glucose Ra) using a constant rate infusion of [6,6-H2]glucose and determined during the last 30 min of the clamp by subtracting glucose Ra from the exogenous glucose infusion rate. Nonoxidative glucose disposal was calculated using indirect calorimetry. Body composition testing was completed using dual energy x-ray absorptiometry., Results: ISGD increased by approximately 20% with HI (Delta of 1.4 +/- 0.5 mg x kg(-1) FFM.min(-1)). However, ISGD did not change (Delta of -0.4 +/- 0.1 mg x kg(-1) FFM.min(-1)) with MI and was not different (Delta of -0.2 +/- 0.1 mg x kg(-1) FFM.min(-1)) in the control group. Nonoxidative glucose disposal increased with HI (Delta of 1.4 +/- 0.5 mg x kg(-1) FFM.min(-1)), but there was no change in nonoxidative glucose disposal with MI or in the control group. No change in body weight or percentage of body fat was observed in any group., Conclusion: In weight-stable subjects, MI resulted in no change in ISGD, and the improvement in ISGD with HI was completely reliant on improvements in nonoxidative glucose disposal.

Background: Previous studies have demonstrated that aerobic exercise training and weight loss have independent effects on insulin-stimulated glucose disposal (ISGD). We hypothesized that ad libitum consumption of a high-carbohydrate diet would result in weight loss and improved ISGD, and that aerobic exercise training would facilitate greater improvements in ISGD compared with diet alone., Methods: Older participants (13 women, 9 men; age = 66 +/- 1 year) with impaired glucose tolerance were randomly assigned to an ad libitum diet alone (18% fat, 19% protein, 63% carbohydrate) or this diet plus aerobic exercise training (4 d/wk, 45 min/d, 80% VO(2peak)) for 12 weeks. ISGD, abdominal fat distribution, muscle glycogen, and glycogen synthase activity were assessed pre- and postintervention., Results: Consumption of the diet resulted in significant weight loss and an improvement in ISGD. Consumption of the diet plus exercise training also resulted in weight loss and increased ISGD, but results were not significantly different from those in the diet-alone group. Mean abdominal visceral and subcutaneous adipose tissue cross-sectional areas were smaller postintervention compared to baseline with no difference between groups. Exercise training and consumption of the diet increased muscle glycogen content (344.7 +/- 21.3 to 616.7 +/- 34.4 micromol.g(-1)) and decreased glycogen synthase activity (0.21 +/- 0.02 to 0.13 +/- 0.01) compared to the diet alone., Conclusions: These results demonstrate that consumption of an ad libitum, high-carbohydrate diet alone or in combination with aerobic exercise training results in weight loss and improved insulin sensitivity. Furthermore, exercise combined with this diet appears to limit additional increases in insulin sensitivity due to muscle glycogen supercompensation with a concomitant adaptive response of glycogen synthase.

Background: The efficacy of ad libitum low-fat diets in reducing body weight and fat in overweight and obese adults remains controversial., Methods: We examined the effect of a 12-week low-fat, high-complex carbohydrate diet alone (HI-CHO) and in combination with aerobic exercise training (HI-CHO + EX) on body weight and composition in 34 individuals with impaired glucose tolerance (20 women and 14 men; mean +/- SEM age, 66 +/- 1 years). Participants were randomly assigned to a control diet (41% fat, 14% protein, 45% carbohydrates, and 7 g of fiber per 1000 kcal), a HI-CHO diet (18% fat, 19% protein, 63% carbohydrates, and 26 g of fiber per 1000 kcal), or a HI-CHO diet plus endurance exercise 4 d/wk, 45 min/d, at 80% peak oxygen consumption (HI-CHO + EX). Participants were provided 150% of estimated energy needs and were instructed to consume food ad libitum. Total food intake, body composition, resting metabolic rate, and substrate oxidation were measured., Results: There was no significant difference in total food intake among the 3 groups and no change in energy intake over time. The HI-CHO + EX and HI-CHO groups lost more body weight (-4.8 +/- 0.9 kg [P=.003] and -3.2 +/- 1.2 kg [P=.02]) and a higher percentage of body fat (-3.5% +/- 0.7% [P=.01] and -2.2% +/- 1.2% [P=.049]) than controls (-0.1 +/- 0.6 kg and 0.2% +/- 0.6%). In addition, thigh fat area decreased in the HI-CHO (P=.003) and HI-CHO + EX (P<.001) groups compared with controls. High carbohydrate intake and weight loss did not result in a decreased resting metabolic rate or reduced fat oxidation., Conclusion: A high-carbohydrate diet consumed ad libitum, with no attempt at energy restriction or change in energy intake, results in losses of body weight and body fat in older men and women.

Aging is associated with a decline in daily energy expenditure that is disproportionately greater than the decline in daily energy intake. Collectively, these events can create a "positive" energy balance, secondary gains in central and total body fat, and a subsequently higher risk of morbidity and mortality. Participation in regular physical activity is a logical strategy to attenuate the decline in energy expenditure with aging, as physical activity can comprise between 10-50% of an older person's daily energy expenditure. Understanding the influence of regular physical activity on energy expenditure with advancing age is clinically relevant, particularly since estimates predict that nearly 25% of the population will be > or = 65 years of age by the year 2030. This brief review will focus on the current state of aging, energy expenditure, and physical activity literature. Topics to be addressed include: (a) measurement of physical activity in older adults; (b) aging and physical inactivity; and (c) influence of regular aerobic exercise on resting metabolic rate (RMR), thermic effect of food (TEF), and non-exercising physical activity.

Objective: African American women have a high prevalence of obesity, which partially may be explained by their lower rates of resting energy expenditure (REE). The aim of this study was to examine the influence of acute sibutramine administration on REE and post-exercise energy expenditure in African American women., Research Methods and Procedures: A total of 15 premenopausal, African American women (age, 29 +/- 5 years; body fat, 38 +/- 7%) completed a randomized, double-blind cross-over design with a 30-mg ingestion of sibutramine or a placebo. Each trial was completed a month apart in the follicular phase and included a 30-minute measurement of REE 2.5 hours after sibutramine or placebo administration. This was followed by 40 minutes of cycling at approximately 70% of peak aerobic capacity and a subsequent 2-hour measurement of post-cycling energy expenditure., Results: There was no difference (p > 0.05) in REE (23.70 +/- 2.81 vs. 23.69 +/- 2.95 kcal/30 min), exercise oxygen consumption (1.22 +/- 0.15 vs. 1.25 +/- 0.15 liter/min), and post-cycling energy expenditure (104.2 +/- 12.7 vs. 104.9 +/- 11.4 kcal/120 min) between the sibutramine and placebo trials, respectively. Cycling heart rate was significantly higher (p = 0.01) during the sibutramine (158 +/- 14 beats/min) vs. placebo (150 +/- 12 beats/min) trials., Discussion: These data demonstrate that acute sibutramine ingestion does not increase REE or post-exercise energy expenditures but does increase exercising heart rate in overweight African American women. Sibutramine may, therefore, impact weight loss through energy intake and not energy expenditure mechanisms.

Controversy exists regarding the association between the Trp64Arg variant of the beta3-adrenoceptor gene and visceral obesity. The cross-sectional nature of most studies, the modest effect of the variant, and sex or ethnic differences between groups have contributed to discrepancies among investigations. To overcome these confounding factors, we examined the effect of the Trp64Arg variant on total and visceral adipose tissue loss, insulin sensitivity, and cardiovascular disease risk factors in response to weight reduction in obese older women. A total of 24 women (age 57 +/- 4 years), including 1 Trp64Arg homozygote, 10 Trp64Arg heterozygotes, and 13 normal homozygotes, were admitted to a weight reduction program of 13 +/- 3 months, with weight and nutritional intake stabilization established before testing. Total and regional adiposity were measured with dual-energy X-ray absorptiometry and computed tomography, insulin sensitivity was measured by the hyperinsulinemic-euglycemic clamp technique, and a blood lipid profile was obtained. No baseline differences were noted in adiposity measurements, glucose disposal, and lipid profiles among carriers and noncarriers of the variant allele. In response to weight loss, carriers and noncarriers of the Trp64Arg allele had similar reductions in body weight (-16.4 +/- 5.0 vs. -14.1 +/- 6.2 kg, NS) and body fat (-10.0 +/- 5.2 vs. -11.5 +/- 3.9 kg, NS). However, loss of visceral adipose tissue was 43% lower in carriers of the Trp64Arg allele compared with noncarriers (-46 +/- 27 vs. -81 +/- 51 cm2, P = 0.05). Furthermore, there was less improvement in the total cholesterol-to-HDL cholesterol ratio (-0.18 +/- 0.54 vs. -0.72 +/- 0.56, P = 0.04) in carriers compared with noncarriers of the allele. Although glucose disposal improved in both groups, there was no difference in the magnitude of improvement between carriers and noncarriers of the variant allele. In conclusion, older obese women carrying the Trp64Arg beta3-adrenoceptor gene variant have an impaired capacity to lose visceral adipose tissue in response to prolonged caloric restriction. Despite these genetic differences in loss of intraabdominal adipose tissue, improvement in glucose disposal was similar between groups.

Older obese postmenopausal women have an increased risk for type 2 diabetes and cardiovascular disease. Increased abdominal obesity may contribute to these comorbidities. There is considerable controversy, however, regarding the effects of visceral adipose tissue as a singular predictor of insulin resistance compared to the other constituents of adiposity. To address this issue, we examined the independent association of regional adiposity and total fat mass with glucose disposal in obese older postmenopausal women. A secondary objective examined the association between glucose disposal with markers of skeletal muscle fat content (muscle attenuation) and physical activity levels. We studied 44 healthy obese postmenopausal women between 50 and 71 yr of age (mean +/- SD, 56.5 +/- 5.3 yr). The rate of glucose disposal was measured using the euglycemic/hyperinsulinemic clamp technique. Visceral and sc adipose tissue areas and midthigh muscle attenuation were measured from computed tomography. Fat mass and lean body mass were estimated from dual energy x-ray absorptiometry. Peak VO2 was measured from a treadmill test to volitional fatigue. Physical activity energy expenditure was measured from indirect calorimetry and doubly labeled water. Pearson correlations indicated that glucose disposal was inversely related to visceral adipose tissue area (r = -0.40; P < 0.01), but not to sc adipose tissue area (r = 0.17), total fat mass (r = 0.05), midthigh muscle attenuation (r = 0.01), peak VO2 (r = -0.22), or physical activity energy expenditure (r = -0.01). The significant association persisted after adjusting visceral adipose tissue for fat mass and abdominal sc adipose tissue levels (r = -0.45; P < 0.005; in both cases). Additional analyses matched two groups of women for fat mass, but with different visceral adipose tissue levels. Results showed that obese women with high visceral adipose tissue levels (283 +/- 59 vs. 137 +/- 24 cm2; P < 0.0001) had a lower glucose disposal per kg lean body mass compared to those with low visceral adipose tissue levels (0.44 +/- 0.14 vs. 0.66 +/- 0.28 mmol/kg x min; P < 0.05). Visceral adipose tissue is an important and independent predictor of glucose disposal, whereas markers of skeletal muscle fat content or physical activity exhibit little association in obese postmenopausal women.

The objective of this study was to examine the importance of cardiorespiratory fitness vs. physical activity energy expenditure on selected cardiovascular disease risk factors in older individuals. One hundred and seventeen older individuals, 53 men (68 +/- 9 yr) and 63 women (67 +/- 7 yr), participated in the study. This cohort was divided into 4 groups: 1) high cardiorespiratory fitness and high physical activity, 2) high cardiorespiratory fitness and low physical activity, 3) low cardiorespiratory fitness and high physical activity, and 4) low cardiorespiratory fitness and low physical activity. Cardiorespiratory fitness (VO2max) was determined from a graded exercise test, physical activity energy expenditure was measured by doubly labeled water and indirect calorimetry, body composition was determined by dual energy x-ray absorptiometry, and dietary practices were determined by a 3-day recall. Cardiorespiratory fitness exerted greater effects on the cardiovascular disease risk profile than physical activity. That is, older individuals with higher levels of cardiorespiratory fitness, regardless of their physical activity levels, showed lower levels of fasting insulin (P < 0.01), triglycerides (P < 0.05), total cholesterol (P < 0.05), total to high density lipoprotein cholesterol ratio (P < 0.05), low density lipoprotein (P < 0.05), and lower waist circumference (P < 0.01). Moreover, individuals with a high cardiorespiratory fitness but low physical activity energy expenditure displayed a more favorable cardiovascular disease risk profile than individuals with low cardiorespiratory fitness and high physical activity energy expenditure. The results suggest that higher levels of cardiorespiratory fitness have greater cardioprotective effects than higher levels of free living physical activity in older individuals. Although these findings do not discount the health benefits of being physically active, it is possible that greater emphasis should be placed on aerobic exercise to increase cardiorespiratory fitness in the elderly.

There is considerable controversy regarding factors regulating free-living physical activity energy expenditure (PAEE) in older individuals. This component is highly variable, is difficult to accurately assess, and reflects both volitional and nonvolitional activities. We examined the association between maximal aerobic fitness (peak VO2) and free-living PAEE in older individuals. One hundred and eighty healthy older patients (96 females and 84 males) between 45-90 yr of age were studied. Total energy expenditure was measured from doubly labeled water. PAEE was calculated as the difference between total energy expenditure, resting metabolic rate, and estimated thermic effect of a meal. Peak VO2 was assessed from an exercise test to volitional fatigue. Fat mass and fat-free mass were assessed from dual energy x-ray absorptiometry. After correction for age, fat mass, and fat-free mass, significant correlations were observed between peak VO2 and PAEE for older males (r = 0.42; P < 0.0001) and females (r = 0.24; P < 0.05), although significant variation among volunteers was noted. When subjects were subdivided by tertiles based on their peak VO2 (liters per min), males with the highest peak VO2 showed greater free-living PAEE than individuals with low peak VO2 (P < 0.01). Similar results were observed in females (P < 0.05). Our results suggest a positive association between higher levels of peak VO2 and greater free-living PAEE in older individuals. This relationship is stronger in older men than in women. These additional energy-dissipating properties during their free-living time may serve to preserve leanness and buffer fat gain with age.

We examined the hypothesis that postmenopausal women with the beta3-adrenoceptor gene variant (Trp64Arg) have reduced total daily energy expenditure (TEE), altered free fatty acid kinetics, and increased intra-abdominal fat. A secondary objective was to examine whether the obese state masks the effect of the variant on resting metabolic rate (RMR). There were 23 obese heterozygous women with the genetic variant (age 58 +/- 6 years; BMI 36 +/- 7 kg/m2) who were compared with 19 homozygous obese women with the normal allele (age 56 +/- 4 years; BMI 36 +/- 3 kg/m2). Daily energy expenditure was determined from doubly labeled water and indirect calorimetry, lipolysis from infusion of [1-13C]palmitate, and body fat distribution from computed tomography. No significant differences were found in TEE, RMR, energy expenditure of physical activity, the thermic effect of a meal, fat oxidation as estimated by fasting and postprandial respiratory quotients (RQs), or rate of lipolysis. Similarly, no difference was found in visceral adipose tissue and abdominal subcutaneous fat areas. When RMR was compared between obese (n = 23) and never-obese women with the Trp64Arg variant (n = 16), we found a 317 kcal/day lower RMR in never-obese women after controlling for fat mass, fat-free mass, and age (P < 0.0017). These results do not support the hypothesis that already obese women with the Trp64Arg polymorphism of the beta3-adrenergic receptor gene have lower daily energy expenditure, altered lipolysis, and increased abdominal obesity. On the other hand, the lower RMR in never-obese women suggests that the obese state may mask a moderate effect of the Trp64Arg variant on energy expenditure. Although these results need to be confirmed in other populations, the obese state may have been a confounding factor in previous studies of the beta3-adrenoceptor Trp64Arg variant and energy expenditure.

We compared the accuracy of two physical activity recall questionnaires and a motion detector in 45- to 84-yr-old women (n = 35) and men (n = 32), using doubly labeled water (DLW) in conjunction with indirect calorimetry as the criterion measure. Subjects were administered the Yale Physical Activity Survey (YPAS) and Minnesota Leisure Time Physical Activity Questionnaire (LTA). Physical activity energy expenditure was determined over a 10-day period by using a Caltrac uniaxial accelerometer and DLW in conjunction with indirect calorimetry. In older women, Minnesota LTA (386 +/- 228 kcal/day) and Caltrac (379 +/- 162 kcal/day) underestimated physical activity by approximately 55% compared with DLW (873 +/- 244 kcal/day). No difference was observed between daily physical activity measured by the YPAS (863 +/- 447 kcal/day) and DLW in older women. In older men, Minnesota LTA (459 +/- 288 kcal/day) and Caltrac (554 +/- 242 kcal/day) underestimated daily physical activity by approximately 50-60% compared with DLW (1,211 +/- 429 kcal/day). No difference was found between physical activity measured by the YPAS (1,107 +/- 612 kcal/day) and DLW in older men. Despite no difference in mean physical activity levels between YPAS and DLW in women and men, Bland and Altman (Lancet 1: 307-310, 1986) analyses demonstrated poor concordance between DLW and YPAS (i.e., limits of agreement = -1,310-1,518 kcal/day). Our data suggest that the Minnesota LTA recall and Caltrac uniaxial accelerometer may significantly underestimate free-living daily physical activity energy expenditure in older women and men. Although the YPAS compares favorably with DLW on a group basis, its use as a proxy measure of individual daily physical activity energy expenditure may be limited in older women and men.

There is controversy regarding the role of the Trp64Arg variant of the beta3-adrenergic receptor (beta3AR) gene in the pathogenesis of insulin resistance. The modest effect of the variant as well as differences in study design, gender, age, and genetic background may contribute to divergent results among investigations. Insulin sensitivity (euglycemic clamp and tracers) was measured in 13 obese women (57 +/- 6 yr old) heterozygous for the beta3AR variant and in 14 women (57 +/- 4 yr old) homozygous for the normal gene. Groups were matched for age, body composition, intraabdominal fat, sc abdominal fat, physical activity level, and aerobic capacity. Exogenous glucose infusion during the clamp was significantly lower (P = 0.03) in beta3AR heterozygotes (241 +/- 135 mg/min) vs. normal homozygotes (379 +/- 172 mg/min). Basal endogenous glucose production was not different (P = 0.20) between heterozygotes (175 +/- 27 mg/min) and normal homozygotes (164 +/- 14 mg/min). Endogenous glucose production during hyperinsulinemia was also not different (P = 0.22) between heterozygotes (77 +/- 57 mg/min) and normal homozygotes (56 +/- 16 mg/min). Total glucose disposal adjusted for residual endogenous glucose production was lower (P = 0.049) for heterozygotes (320 +/- 111 mg/min) than for normal homozygotes (441 +/- 183 mg/min). Our results suggest that obese postmenopausal women who are heterozygous for the Trp64Arg variant in the beta3AR gene have greater insulin resistance than age-, body composition-, and physical activity-matched women homozygous for the normal gene.

Determinants of daily energy needs and physical activity are unknown in free-living elderly. This study examined determinants of daily total energy expenditure (TEE) and free-living physical activity in older women (n = 51; age = 67 +/- 6 yr) and men (n = 48; age = 70 +/- 7 yr) by using doubly labeled water and indirect calorimetry. Using multiple-regression analyses, we predicted TEE by using anthropometric, physiological, and physical activity indexes. Data were collected on resting metabolic rate (RMR), body composition, peak oxygen consumption (VO2 peak), leisure time activity, and plasma thyroid hormone. Data adjusted for body composition were not different between older women and men, respectively (in kcal/day): TEE, 2,306 +/- 647 vs. 2,456 +/- 666; RMR, 1,463 +/- 244 vs. 1,378 +/- 249; and physical activity energy expenditure, 612 +/- 570 vs. 832 +/- 581. In a subgroup of 70 women and men, RMR and VO2 peak explained approximately two-thirds of the variance in TEE (R2 = 0.62; standard error of the estimate = +/-348 kcal/day). Crossvalidation of this equation in the remaining 29 women and men was successful, with no difference between predicted and measured TEE (2,364 +/- 398 and 2,406 +/- 571 kcal/day, respectively). The strongest predictors of physical activity energy expenditure (P < 0.05) for women and men were VO2 peak (r = 0.43), fat-free mass (r = 0.39), and body mass (r = 0.34). In summary, RMR and VO2 peak are important independent predictors of energy requirements in the elderly. Furthermore, cardiovascular fitness and fat-free mass are moderate predictors of physical activity in free-living elderly.

We examined daily energy requirements and determinants of physical activity in older, free-living African-American women (n = 37; age, 64 +/- 8 yr) and men (n = 28; age, 64 +/- 7 yr). Total daily energy expenditure and its components [i.e. resting metabolic rate (RMR) and physical activity energy expenditure] were determined using doubly labeled water and indirect calorimetry. Body composition from dual energy x-ray absorptiometry, maximal oxygen consumption from a graded treadmill test, and leisure time physical activity from a structured interview were determined. Total daily energy expenditure adjusted for body composition was lower (P < 0.05) for women (2198 +/- 621 kcal/d) than for men (2633 +/- 669 kcal/d) due to a lower RMR (1431 +/- 240 vs. 1576 +/- 259 kcal/d; P = 0.07) and physical activity energy expenditure (548 +/- 559 vs. 794 +/- 603 kcal/d; P = 0.19), respectively. The physical activity level ratio (i.e. total daily energy expenditure/RMR) was not different from Food and Agriculture Organization/World Health Organization/United Nations University recommendations (i.e. 1.51) for women (1.51 +/- 0.25), but was higher for men (1.71 +/- 0.32). The strongest correlates with physical activity energy expenditure were age for women (r = -0.44; P < 0.01) and maximal oxygen consumption for men (r = 0.39; P < 0.05). These data show that daily energy requirements are significantly lower in African-American women compared to men, primarily due to lower levels of physical activity energy expenditure. Furthermore, lower levels of cardiovascular fitness in men and advancing age in women are associated with lower physical activity energy expenditure.

The prevalence of obesity is increasing rapidly in the US and other developed countries. Even though the percentage of older individuals is increasing worldwide, obesity has only recently become a recognised problem in this population. Obesity occurs when energy intake chronically exceeds energy expenditure. Moreover, advancing age is associated with an inability to couple energy intake with energy expenditure. Obesity contributes to many adverse health outcomes, including non-insulin-dependent (type II) diabetes mellitus, as well as to an increase in both cardiovascular and all-cause mortality. Only recently has the medical community begun to accept obesity as a disease with a multifactorial pathogenesis that requires systematic lifestyle changes and pharmacological treatment. Several groups of drugs are available for the pharmacotherapy of obesity; anorectic medications (e.g. fenfluramine, dexfenfluramine); substances affecting energy expenditure and body composition [e.g. chromium (chromium picolinate), ephedrine, anabolic steroids, beta 3-adrenoceptor agonists]; and drugs affecting the absorption of nutrients (e.g. orlistat). To date, few drugs have produced and sustained a significant bodyweight loss. However, some drugs induce a significant short term reduction in bodyweight compared with placebo. Moreover, there is a paucity of information regarding the effectiveness of these drugs in the treatment of obesity in the elderly. Furthermore, it is even debated whether obesity should be treated with drug intervention in the elderly. Clinicians prescribing medications for obesity treatment in the elderly need to carefully consider the benefit: risk ratio, given the high prevalence of polypharmacy in elderly patients. Furthermore, physiological changes that occur with aging may affect the pharmacokinetics of administered drugs and need to be taken into consideration.

The purpose of this investigation was to examine the effects of diet on muscle triglyceride and endurance performance. Seven endurance-trained men completed a 120-min cycling bout at 65% of maximal oxygen uptake. Each subject then ingested an isocaloric high-carbohydrate (Hi-CHO; 83% of energy) or a high-fat (Hi-Fat; 68% of energy) diet for the ensuing 12 h. After a 12-h overnight fast, a 1,600-kJ self-paced cycling bout was completed. Muscle triglyceride measured before (33.0 +/- 2.3 vs. 37.0 +/- 2.1 mmol/kg dry wt) and after (30.9 +/- 2.4 vs. 32.8 +/- 1.6 mmol/kg dry wt) the 120-min cycling bout was not different between the Hi-CHO and Hi-Fat trials, respectively. After the 24-h dietary-fasting period, muscle triglyceride was significantly higher for the Hi-Fat (44.7 +/- 2.4 mmol/kg dry wt) vs. the Hi-CHO (27.5 +/- 2.1 mmol/kg dry wt) trial. Furthermore, self-paced cycling time was significantly greater for the Hi-Fat (139.3 +/- 7.1 min) compared with the Hi-CHO (117.1 +/- 3.2 min) trial. These data demonstrate that there was not a significant difference in muscle triglyceride concentration before and after a prolonged moderate-intensity cycling bout. Nevertheless, a high-fat diet increased muscle triglyceride concentration and reduced self-paced cycling performance 24 h after the exercise compared with a high-carbohydrate diet.

The primary purpose of the study was to compare maximal accumulated oxygen deficit (MAOD) in resistance-trained (RT), endurance-trained (ET), and untrained men (UT). A secondary purpose was to determine the influence of leg muscle mass (MM) on MAOD by examining the relationship between MM and MAOD and by comparing MAOD expressed relative to MM between the groups. MAOD was determined during 2-4 min of constant-load fatiguing cycling. MM, estimated via anthropometric measurements, was higher (p < .05) for RT (mean +/- SE; 25.5 +/- 3.4 kg) compared to ET (20.3 +/- 3.5) and UT (21.6 +/- 3.4). MAOD in liters O2eq was larger in RT (4.75 +/- 0.3) compared to UT (3.07 +/- 0.3) and ET (3.75 +/- 0.3). A significant positive correlation was observed between MAOD (LO2eq) and MM (kg) for RT only (RT, r = .85; ET, r = .55; UT, r = .20). Based on the correlational and mean MM data, the higher MAOD (LO2eq) in RT relative to ET and UT is predominantly the result of their larger leg muscle mass.

The present study was designed to evaluate the influence of starch structure on muscle glycogen resynthesis and cycling performance. Eight male cyclists (22 +/- 1 yr) completed an exercise protocol (DP) to decrease vastus lateralis glycogen concentration. This exercise consisted of 60 min cycling at 75% VO2max, followed by six 1-min sprints at approximately 125% VO2max with 1 min rest intervals. In the 12 hr after the exercise each subject consumed approximately 3000 kcal (65:20:15% carbohydrate, fat and protein). All of the carbohydrate (CHO) consumed was derived from one of four solutions; 1) glucose, 2) maltodextrin (glucose polymer), 3) waxy starch (100% amylopectin), or 4) resistant starch (100% amylose). Muscle biopsies were taken from the vastus lateralis muscle after DP and 24 hr later to determine glycogen concentrations. A 30 min cycling time trial (TT) was performed following the 24 hr post-DP muscle biopsy to examine the influence of the feeding regimen on total work output. The post-DP glycogen concentrations were similar among the four trials, ranging from 220.3 +/- 29.2 to 264 +/- 48.3 mmol.kg-1 dry weight (d.w.) muscle. Twenty-four hours after DP, muscle glycogen concentration had increased less (p < 0.05) in the resistant starch trial (+90.8 +/- 12.8 mmol.kg-1 d.w.) than in the glucose (+197.7 +/- 31.6 mmol.kg-1 d.w.), maltodextrin (+136.7 +/- 24.5 mmol.kg-1 d.w.) and waxy starch (+171.8 +/- 37.1 mmol.kg-1 d.w.) trials. There were no differences in total work output during the TT, or blood lactate concentration immediately following the TT in any of the CHO trials. In summary, glycogen resynthesis was attenuated following ingestion of starch with a high amylose content, relative to amylopectin or glucose; however, short duration time trial performance was unaffected.

This study compared the physiological responses and performance following the ingestion of a waxy starch (WS), resistant starch (RS), glucose (GL) and an artificially-sweetened placebo (PL) ingested prior to exercise. Ten college-age, male competitive cyclists completed four experimental protocols consisting of a 30 min isokinetic, self-paced performance ride preceded by 90 min of constant load cycling at 66% VO2max. Thirty min prior to exercise, they ingested 1 g.kg-1 body weight of GL, WS, RS, or PL At rest, GL elicited greater (p < 0.05) serum glucose and insulin responses than all other trials. During exercise, however, serum glucose, insulin, blood C-peptide and glucagon responses were similar among trials. The mean total carbohydrate oxidation rates (CHOox) were higher (p < 0.05) during the GL, WS, and RS trials (2.59 +/- 0.13, 2.49 +/- 0.10, and 2.71 +/- 0.15 g.min-1, respectively) compared to PL (2.35 +/- 0.12 g.min-1). Subjects were able to complete more work (p < 0.05) during the performance ride when they ingested GL (434 +/- 25.2 kj) or WS (428 +/- 22.5 kj) compared to PL (403 +/- 35.1 kj). They also tended to produce more work with RS ingestion (418 +/- 31.4 kj), although this did not reach statistical significance (p < 0.09). These results indicate that preexercise CHO ingestion in the form of starch or glucose maintained higher rates of total carbohydrate oxidation during exercise and provided an ergogenic benefit during self-paced cycling.

The purpose of this study was to determine the effect of 12 wks of aerobic training on resting lymphocyte number and proliferation, and immunoglobulin and cytokine levels. Eleven college-aged males (training group = EX) performed 30 min of cycling at 75% of VO2peak, 3 days/wk with VO2peak assessment and blood samples taken at 0,8 and 12 wks. A group of 10 sedentary controls (CT) underwent the same testing protocol. Lymphocyte proliferation response to phytohemagglutinin (PHA) and pokeweed mitogen (PWM) was quantified as a stimulation index (SI) based on the ratio of stimulated versus control cultures, and as total counts per min (CPM). Immunoglobulin (Ig) levels (IgG, IgA, and IgM), and lymphocyte counts were also determined. There was a significant increase in VO2 in the EX group (41.0 +/- 1.8 vs. 46.3 +/- 1.4 ml.kg-1.min-1 pre and post training, respectively). Training had no effect on the PHA SI for the EX group (23.9 +/- 3.3, 27.7 +/- 4.1, and 26.3 +/- 4.0 at 0, 8 and 12 wks, respectively), or the responses of the CT group (28.8 +/- 6.0, 23.9 +/- 3.1, and 30.6 +/- 4.3). No changes were observed for the PWM SI. Significant increases were observed in the CPM for both groups. No differences in the Ig or lymphocyte levels were found during the study. These data indicate that 12 wks of moderate endurance training did not alter resting immune function as determined by mitogen stimulated lymphocyte proliferation, total circulating lymphocytes, or Ig levels.

The purpose of this investigation was to determine the effect of caffeine ingestion on work output at various levels of perceived exertion during 30 min of isokinetic variable-resistance cycling exercise. Ten subjects completed six trials 1 hr after consuming either 6 mg.kg-1 caffeine (3 trials) or a placebo (3 trials). During each trial the subjects cycled at what they perceived to be a rating of 9 on the Borg rating of perceived exertion scale for the first 10 min, a rating of 12 for the next 10 min, and a rating of 15 for the final 10 min. Total work performed during the caffeine trials averaged 277.8 +/- 26.1 kJ, whereas the mean total work during the placebo trials was 246.7 +/- 21.5 kJ (p < .05). However, there were no significant differences between the conditions in respiratory exchange ratio. These data suggest that caffeine may play an ergogenic role in exercise performance by altering both neural perception of effort and substrate availability.

The purpose of the study was to compare changes in running economy, foot impact shock, run performance, and resting heart rate and blood pressure elicited by increases in training volume via run training (RT) and cross training (CT). After 30 d of normal training (NT), male runners (N = 11) completed two 10 d periods of increased training each preceded by 14 d of reduced training (80% NT). Subjects ran 10 consecutive days in the afternoon (100% of NT) and performed 8 additional workouts in the morning (100% of NT). The morning sessions were performed on a cycle ergometer (CT) or a treadmill (RT). Running economy, foot impact shock and lactate were assessed during submaximal running (3.9 +/- 0.06 m.sec-1) at D0 and D11. Following the submaximal run, subjects completed a simulated 5 km race on a treadmill. VO2 during the running economy test was significantly higher at D11 of CT (52.5 +/- 1.5) compared to RT (51.1 +/- 1.4 ml.kg-1.min-1). RER, carbohydrate oxidation, and lactate were significantly lower; whereas, foot impact shock was significantly higher following both training modes. No significant changes in run performance, resting heart rate and blood pressure occurred during the study. In summary, 10 d of increased training resulted in a reduced running economy for CT, and a lower carbohydrate oxidation and an increase in foot impact shock for both training modes.

Muscle carnitine levels were examined in 31 younger [mean (SD), 27 (5) years] and 27 older [49 (8) years] men. Needle biopsies were obtained from the lateral gastrocnemius or vastus lateralis muscles and assayed for free and total carnitine concentrations via a 5,5'-Dithiobis-(2-nitrobenzoic acid) DTNB-linked spectrophotometric procedure. A subgroup of subjects (n = 28) were assessed for citrate synthase (CS) and succinate dehydrogenase (SDH) activity, and type I muscle fiber composition (% type I fibers). An additional sub-group of nine subjects was assessed for free and total serum carnitine levels. No mean (SEM) differences in free [21.6 (0.7) vs 20.3 (0.9) mumol.g dry weight-1] and total [26.4 (0.6) vs 26.1 (0.9) mumol.g dry weight-1) muscle carnitine levels were found between the younger and older subjects, respectively. Correlational data revealed no significant relationships between total muscle carnitine and CS (r = -0.36), SDH (r = -0.26), or % type I fibers (r = -0.16). In addition, there was a low non-significant relationship between serum and muscle total carnitine concentrations (r = -0.44). These findings suggest that muscle carnitine levels are similar between younger and older males, and there does not appear to be any relationship between muscle carnitine and markers of muscle oxidative potential (i.e., oxidative enzymes, % type I fiber). Since serum carnitine is often used as an indicator of body carnitine status, it is noteworthy that we found a low negative relationship between blood and muscle carnitine concentrations.

The purpose of this study was to examine the effects of different drink volumes on rehydration, gastric emptying, and markers of fluid balance following exercise-induced dehydration. Nine male subjects (27.3 +/- 5.47 yr of age, 77.8 +/- 7.9 kg) exercised for 90 min (or until 2.5% of initial body weight was lost) on a cycle ergometer in a hot environment (30 degrees C with 60% RH). Following exercise, subjects were moved to a neutral environment (23 degrees C 50% RH) and rested for 30 min prior to beginning a 3-h rehydration period. During rehydration, subjects were serially fed with an electrolyte solution (14.98 mmol.l-1 Na+, 13.51 mmol.l-1 Cl-, and 7.95 mmol.l-1 K+) every 30 min with either 100% or 150% of the fluid lost during exercise. Gastric contents were determined every 15 min using double sampling. Blood samples, urine samples, and body weights were taken before and after exercise and at 1-h intervals throughout rehydration. Blood samples were analyzed for percent change in plasma volume, electrolyte concentration, aldosterone levels, and renin activity. Urine electrolyte concentrations were also measured. The final percent rehydration was 48.11 and 67.90 for the 100% and 150% conditions, respectively. During rehydration, the subjects emptied 98.9 and 86.0% of the fluid ingested, and the % emptied and used for weight gain at the end of rehydration was 55.1 and 54.6 for the 100% and 150% trials, respectively. Urine production was significantly higher in the 150 compared with the 100% condition while renin and aldosterone levels did not differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)