Effects of resistance or aerobic exercise training on total and regional body composition in sedentary overweight middle-aged adults

The purpose of this study was to examine the effects of 10 weeks of aerobic endurance training (AET), resistance exercise training (RET), or a control (CON) condition on absolute and relative fat mass (FM) or fat-free mass (FFM) in the total body (TB) and regions of interest (ROIs) of sedentary overweight middle-aged males and females. Following prescreening, 102 subjects underwent anthropometric measurements, dual-energy X-ray absorptiometry, and strength and aerobic exercise testing. Randomized subjects (male RET, n = 16; female RET, n = 19; male AET, n = 16; and female AET, n = 25) completed supervised and periodized exercise programs (AET, 30-50 min cycling at 70%-75% maximal heart rate; RET, 2-4 sets × 8-10 repetitions of 5-7 exercises at 70%-75% 1 repetition maximum) or a nonexercising control condition (male CON, n = 13 and female CON, n = 13). Changes in absolute and relative TB-FM and TB-FFM and ROI-FM and ROI-FFM were determined. At baseline, and although matched for age and body mass index, males had greater strength, aerobic fitness, body mass, absolute and relative TB-FFM and ROI-FFM, but reduced absolute and relative TB-FM and ROI-FM, compared with females (p < 0.05). After training, both female exercise groups showed equivalent or greater relative improvements in strength and aerobic fitness than did the male exercise groups (p < 0.05); however, the male exercise groups increased TB-FFM and reduced TB-FM more than did the female exercise groups (p < 0.05). Male AET altered absolute FM more than male RET altered absolute FFM, thus resulting in a greater enhancement of relative FFM. Despite equivalent or greater responses to RET or AET by female subjects, the corresponding respective increases in FFM or reductions in FM were lower than those in males, indicating that a biased dose-response relationship exists between sexes following 10 weeks of exercise training.     

A weight reduction program preserves fat-free mass but not metabolic rate in obese adolescents

OBJECTIVE: To determine the effects of a multidisciplinary weight reduction program on body composition and energy expenditure (EE) in severely obese adolescents. RESEARCH METHODS AND PROCEDURES: Twenty-six severely obese adolescents, 12 to 16 years old [mean BMI: 33.9 kg/m(2); 41.5% fat mass (FM)] followed a 9-month weight reduction program including moderate energy restriction and progressive endurance and resistance training. Body composition was assessed by DXA, basal metabolic rate by indirect calorimetry, and EE by whole-body indirect calorimetry with the same activity program over 36-hour periods before starting and 9 months after the weight reduction period. RESULTS: Adolescents gained (least-square mean +/- SE) 2.9 +/- 0.2 cm in height, lost 16.9 +/- 1.3 kg body weight (BW), 15.2 +/- 0.9 kg FM, and 1.8 +/- 0.5 kg fat-free mass (FFM) (p < 0.001). Basal metabolic rate, sleeping, sedentary, and daily EE were 8% to 14% lower 9 months after starting (p < 0.001) and still 6% to 12% lower after adjustment for FFM (p < 0.05). Energy cost of walking decreased by 22% (p < 0.001). The reduction in heart rate during sleep and sedentary activities (-10 to -13 beats/min), and walking (-20 to -25 beats/min) (p < 0.001) resulted from both the decrease in BW and physical training. DISCUSSION: A weight reduction program combining moderate energy restriction and physical training in severely obese adolescents resulted in great BW and FM losses and improvement of cardiovascular fitness but did not prevent the decline in EE even after adjustment for FFM.     

Effect of a 10-week strength training program and recovery drink on body composition, muscular strength and endurance, and anaerobic power and capacity

OBJECTIVE: We investigated whether postexercise consumption of a supplement containing whey protein, amino acids, creatine, and carbohydrate combined with a strength training program promotes greater gains in fat-free mass (FFM), muscle strength and endurance, and anaerobic performance compared with an isocaloric, carbohydrate-only control drink combined with strength training. METHODS: The study was double blind and randomized, and the experimental supplement was compared with a carbohydrate-only control. Forty-one males (n = 20 in control group, n = 21 in the supplement group; mean age, 22.2 y) participated in a 4 d/wk, 10-wk periodized strength training program. Subjects had to complete at least 70% of the workouts. Before and after 10 wk of strength training, subjects were tested for body composition by using hydrostatic weighing and skinfold thicknesses, one repetition maximum strength and muscular endurance for the bench press and 45-degree leg press, and anaerobic performance using a 30-s Wingate test. Thirty-three subjects (80.5%) completed the training program (n = 15 in control group, n = 18 in the supplement); these 33 subjects also completed all post-training test procedures. Data were analyzed with two-way analysis of variance with repeated measures on time. P <== 0.05 was set as statistically significant. All statistical analyses, including calculation of effect size and power, were completed with SPSS 11.0. RESULTS: Across groups, FFM increased during 10 wk of strength training. Although there was no statistically significant time x group interaction for FFM, there was a trend toward a greater increase in FFM for the supplement group (+3.4 kg) compared with the control group (+1.5 kg; P = 0.077). The effect size (eta(2) = 0.100) was moderately large. Percentage of body fat declined and fat mass was unchanged; there were no differences between groups. One repetition maximum strength for the bench press and 45-degree leg press increased, but there were no differences between groups. Muscular endurance expressed as the number of repetitions completed with 85% of the one repetition maximum was unchanged; external work, which was estimated as repetitions completed x resistance used, increased for the 45-degree leg press but not for the bench press over the 10-wk training period; there were no time x group interactions for either measurement. Anaerobic power and capacity improved, but there were no differences between groups for these variables or for fatigue rate. CONCLUSIONS: Consumption of a recovery drink after strength training workouts did not promote greater gains in FFM compared with consumption of a carbohydrate-only drink; however, a trend toward a greater increase in FFM in the supplement group suggests the need for longer-term studies. Performance variables such as muscle strength and endurance and anaerobic performance were not improved when compared with the carbohydrate-only group.     

Resting metabolic rate and coronary-heart-disease risk factors in aerobically and resistance-trained women.

This cross-sectional study compared physical characteristics, cardiovascular risk factors, and resting metabolic rate (RMR) in a cohort of 82 young women separated into three groups: sedentary (SED, n = 48), aerobically trained (AT, n = 21), and resistance trained (RT, n = 13). Body mass and fat-free mass (FFM) were not different between groups whereas percent body fat was lower in the AT (16.2 +/- 0.7%) and RT (14.7 +/- 0.8%) groups than in the SED group (21.8 +/- 0.8%). There were no between-group differences for blood pressure or blood lipids. RMRs (kJ/min) for the AT (4.31 +/- 0.06) and RT (4.25 +/- 0.09) groups were significantly greater than those for the SED group (3.99 +/- 0.05). When adjusted for differences in FFM, RMRs for the AT group (4.24 +/- 0.05) were different from those of both the RT (4.13 +/- 0.05) and SED (4.05 +/- 0.03) groups; RMRs for the RT and SED groups were not different from each other. No differences were found in cardiovascular risk in young nonobese women of differing exercise status. Aerobic training in young women seems to increase the rate of metabolic activity of resting tissues whereas resistance training does not.     

Evaluation of anthropometric equations to assess body-composition changes in young women

BACKGROUND: Healthy young women who engage in an exercise program may lose fat that is not reflected in body weight changes because of concurrent gains in fat-free mass (FFM). OBJECTIVE: This study addressed the question of how well anthropometry-based predictive equations can resolve these changes. DESIGN: Several widely used skinfold-thickness- or circumference-based equations were compared by using dual-energy X-ray absorptiometry to study 150 healthy young women before and after 8 wk of Army basic combat training (average energy expenditure: 11.7 MJ/d). RESULTS: Women lost 1.2 +/- 2.6 kg fat (mean +/- SD) and gained 2.0 [corrected] +/- 1.5 kg FFM. Fat loss (r = 0.47), but not FFM gain (r = 0.01), correlated with initial fatness. Thus, for many women who lost fat, body weight did not change or increased. Fat loss was associated with a reduction in abdominal circumference but this alone was not a consistent marker of fat loss. One circumference equation and one skinfold-thickness equation yielded the smallest residual SDs (2.0% and 1.9% body fat, respectively) compared with the other equations in predicting body fat. The sensitivity and specificity of the best equations in predicting changes in percentage body fat were not better than 55% and 66%, respectively. CONCLUSIONS: These data suggest that for women, anthropometry can provide better estimates of fatness than body mass index but it is still relatively insensitive to short-term alterations in body composition. Not surprisingly, the circumference equation that includes the most labile sites of female fat deposition (ie, waist and hips instead of upper arm or thigh) proved to be the most reliable.     

Eight-year longitudinal changes in body composition in healthy Swiss adults

OBJECTIVE: Significant changes in body composition occur during lifetime. This longitudinal study (8.0 +/- 0.8 yrs) in a cohort of healthy sedentary and physically active men (n = 78) and women (n = 53), aged 20 to 74 yr describes: 1) the longitudinal changes in weight and body composition and 2) their associations with age and physical activity. Method: Fat-free mass (FFM) and body fat (BF) were assessed by bioelectrical impedance analysis (BIA). Subjects who regularly performed >3 hours per week of endurance type physical activity were classified as "Active". Others were classified as "Sedentary". Subjects were also separated by age (<45 yr vs > or =45 yr). RESULTS: FFM increased by 1.7 +/- 2.8 kg in men <45 yr who gained 4.0 +/- 5.0 kg of body weight and was maintained (0.5 +/- 1.6 kg) in women <45 y who gained 1.6 +/- 3.0 kg of weight. A weight gain of 1.2 +/- 3.3 kg in men > or =45 yr was accompanied by stable FFM (-0.1 +/- 2.3 kg), and of 1.0 +/- 3.2 kg was accompanied by a loss of FFM in women > or =45 yr. In active men > or =45 yr, maintenance of FFM was associated with smaller weight gains than in sedentary; sedentary men > or =45 yr decreased FFM with larger weight gains than active subjects. Sedentary women <45 yr were able to gain FFM; the active women maintained, but did not gain FFM with smaller weight gains than in sedentary women. FFM decreased in >/=45 yr women despite of small weight gains. CONCLUSION: Weight change is clearly associated with a change in FFM. Weight gain is necessary to offset age-related FFM loss between 20 and 74 yrs. In active men, a FFM increase was associated with less weight gain than sedentary men. Future studies should evaluate the threshold of weight change and the level of physical activity necessary to prevent age-related losses of FFM.     

Effects of a very-low-calorie diet and physical-training regimens on body composition and resting metabolic rate in obese females

Sixty-nine obese females received 90 d of a liquid diet providing 2184 kJ/d in clinical trials. Groups were diet only (C), diet plus endurance exercise (EE), diet plus weight training (WT), or diet plus endurance exercise and weight training (EEWT). Changes in body weight, percent fat, fat weight, and fat-free mass were not different between groups. Declines in resting metabolic rate (RMR) were approximately 7% to approximately 12% of baseline values with no differences among groups. A significant increase in work capacity (approximately 16%) was shown for EEWT. Strength index showed declines of approximately 6% for C and EE and gains of approximately 3% and approximately 10% for EEWT and WT, respectively. These clinical trials did not show advantages of any exercise regimen over diet alone for weight loss, body-composition changes, or declines in RMR. Improvements in work capacity were limited and strength improved in groups that participated in strength training.     

Energy expenditure before and during energy restriction in obese patients

Twenty-four hour energy expenditure (24 EE), resting metabolic rate (RMR), spontaneous physical activity and body composition were determined in 7 obese patients (5 females, 2 males, 174 +/- 9% IBW, 38 +/- 2% fat mass) on 2 different occasions: before weight reduction, and after 10 to 16 weeks on a hypocaloric diet as outpatients, the recommended energy intake varying from 3500 to 4700 kJ/day depending on the subject. Mean body weight loss was 12.6 +/- 1.9 kg, ie 13% of initial body weight, 72% being fat. Twenty-four hour energy expenditure (24 EE) was measured in a respiration chamber with all the subjects receiving 10418 kJ/d before weight reduction and an average of 3360 +/- 205 kJ/d while on the diet. When expressed in absolute values, both 24 EE and RMR decreased during the hypocaloric diet from 9819 +/- 442 to 8229 +/- 444 and from 7262 +/- 583 to 6591 +/- 547 kJ/d respectively. On the basis of fat-free-mass (FFM), 24 EE decreased from 168 +/- 6 to 148 +/- 5 kJ/kg FFM/d whereas RMR was unchanged (approximately 120 kJ/kg FFM/d). Approximately one half of the 24 EE reduction (1590 kJ/d) was accounted for by a decrease in RMR, the latter being mainly accounted for by a reduction in FFM. Most of the remaining decline in 24 EE can be explained by a decreased thermic effect of food, and by the reduced cost of physical activity mainly due to a lower body weight. Therefore, there seems little reason to evoke additional mechanisms to explain the decline in energy expenditure during dieting.     

Effect of 3 weeks of detraining on the resting metabolic rate and body composition of trained males

OBJECTIVE: To examine the hypothesis that detraining decreases the resting metabolic rate (RMR) of long-term exercisers. DESIGN: Eight pairs of subjects were matched for age, mass and training volume. They were then randomly allocated to either a control group (continue normal training) or detraining group (stop normal training but continue activities of daily living). SETTING: Exercise Physiology Laboratory, The Flinders University of South Australia. SUBJECTS: Sixteen male subjects (age 23.1 +/- 4.7 y (s.d.); mass 73.73 +/- 8.9 kg; VO2max 60.2 +/- 6.3 ml. kg-1.min-1; height 180.3 +/- 5.0 cm; body fat 14.6 +/- 5.4%) were selected from a pool of respondents to our advertisements. INTERVENTIONS: Each pair of subjects was measured before and after a 3-week experimental period. RESULTS: Two (groups) x 3 (2-, 3-and 4-compartment body composition models) ANOVAs were conducted on the difference between the pre- and post-treatment scores for percentage body fat, fat-free mass (FFM) and relative RMR (kJ.kg FFM-1.h-1). No significant between-group differences were identified except for the detraining group's small decrease in FFM (0.7 kg, P = 0.05). The main effects for body composition model were all significant; but the overall differences between the multicompartment models and the 2-compartment one were less than their technical errors of measurement. No significant interaction (P = 0.51) resulted from a 2 x 2 ANOVA on the pre- and post-treatment absolute RMR data for the control (315.2 and 311.9 kJ/h) and detraining groups (325.4 and 325.5 kJ/h). CONCLUSIONS: 3-weeks detraining is not associated with a decrease in RMR (kJ/h, kJ.kg FFM-1.h-1) in trained males; hence, our data do not support a potentiation of the RMR via exercise training. The greater sensitivity of the multicompartment models to detect changes in body composition was of marginal value.     

Impact of differing protein sources and a creatine containing nutritional formula after 12 weeks of resistance training

OBJECTIVE: We evaluated whether colostrum (Col) or an isocaloric and isonitrogenous blend of whey and casein in addition to creatine (Cr) affects body composition, muscular strength and endurance, and anaerobic performance during resistance training. METHODS: Forty-nine resistance-trained subjects participated in a standardized 12-wk total body resistance training program. In a double-blind and randomized manner, subjects supplemented their diet with a protein control (Pro), Pro/Col, Pro/Cr, or Col/Cr. Supplements were isocaloric and isonitrogenous and provided 60 g/d of casein/whey (Pro) or Col as the protein source. At 0, 8, and 12 wk of supplementation, subjects were weighed, had body composition determined using dual-energy X-ray absorptiometry (DXA), performed one-repetition maximum (1RM) and 80% of 1RM tests on the bench press and leg press, and 30-s anaerobic sprint capacity tests. Data (mean +/- SD) were analyzed by repeated measures analysis of variance and reported as raw data in all tables and as changes from baseline for all figures for the Pro, Pro/Col, Pro/Cr, and Col/Cr groups, respectively. RESULTS: Resistance training increased 1RM strength, muscular endurance, and anaerobic sprint capacity equally in all groups. Significant main and interaction effects (P < 0.05) were found for body mass, DXA total scanned mass, and fat-free mass (FFM; lean plus bone), whereas no changes (P > 0.05) were noted for fat mass, percent fat, or bone content. Post hoc analysis showed that, compared with Pro, subjects ingesting Pro/Col, Pro/Cr, and Col/Cr showed greater gains in body mass and DXA total scanned mass. Subjects ingesting Pro/Cr and Col/Cr had greater increases in FFM during training in comparison with Pro/Col. CONCLUSION: In conjunction with 12 wk of resistance training, ingestion of Col or a blend of whey and casein protein with a vitamin/mineral supplement containing Cr resulted in greater improvements in FFM in comparison with Pro and Pro/Col.     

Nutritional supplementation of the leucine metabolite beta-hydroxy-beta-methylbutyrate (hmb) during resistance training

The effects of supplementation of the leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) were examined in a resistance training study. Thirty-nine men and 36 women between the ages of 20-40 y were randomized to either a placebo (P) supplemented or HMB supplemented (3.0 g HMB/d) group in two gender cohorts. All subjects trained three times per week for 4 wk. In the HMB group, plasma creatine phosphokinase levels tended to be suppressed compared to the placebo group following the 4 wk of resistance training (HMB:174. 4 +/- 26.8 to 173.5 +/- 17.0 U/L; P:155.0 +/- 20.8 to 195.2 +/- 23.5 U/L). There were no significant differences in strength gains based on prior training status or gender with HMB supplementation. The HMB group had a greater increase in upper body strength than the placebo group (HMB:7.5 +/- 0.6 kg; P:5.2 +/- 0.6 kg; P = 0.008). The HMB groups increased fat-free weight by 1.4 +/- 0.2 kg and decreased percent fat by 1.1% +/- 0.2% while the placebo groups increased fat-free weight by 0.9 +/- 0.2 kg and decreased percent fat by 0.5% +/- 0.2% (fat-free weight P = 0.08, percent fat P = 0.08, HMB compared to placebo). In summary, this is the first short-term study to investigate the roles of gender and training status on the effects of HMB supplementation on strength and body composition. This study showed, regardless of gender or training status, HMB may increase upper body strength and minimize muscle damage when combined with an exercise program.     

The effects of a 20-week exercise training program on resting metabolic rate in previously sedentary, moderately obese women

The present study was designed to investigate the effects of exercise training on resting metabolic rate (RMR) in moderately obese women. It was hypothesized that exercise training would increase resting metabolic rate. Nineteen previously sedentary, moderately obese women (age = 38.0 +/- 0.9 years, percent body fat = 37.5 +/- 0.8) trained for 20 weeks using either resistance training (RT) or a combination of resistance training and walking (RT/W). The high intensity resistance-training program was designed to increase strength and fat-free mass and the walking program to increase aerobic capacity. There was also a non-exercising control group (C) of 9 subjects in this study. Fat-free mass was significantly increased in both the RT (+1.90 kg) and RT/W (+1.90 kg) groups as a result of the training program. No group showed significant changes in fat mass or relative body fat from pre- to post-training. Aerobic capacity was slightly, though significantly, increased in the RT/W group only. The RT group showed a significant increase (+44 kcal x day(-1)), while the RT/W group showed a significant decrease (-53 kcal x day(-1)) in resting metabolic rate post-training. RT can potentiate an increase in RMR through an increase in fat-free mass, and the decrease in RMR in the RT/W group may have been a result of heat acclimation from the walk training.     

Assessment of body composition by bioelectrical impedance in a population aged greater than 60 y

Body composition was measured in a group of 35 healthy men and 37 healthy women aged 60-83 y. Body mass index (BMI) in men was 25.0 +/- 2.2 kg/m2 (means +/- SD) and in women, 25.9 +/- 3.2 kg/m2. BMI was low in relation to body fat percentage as determined by skinfold-thickness measurements or densitometry in comparison with the relation found in younger adults. Mean body fat percentage of the male subjects (aged 70.4 +/- 5.2 y) as determined by densitometry was 31.0 +/- 4.5%, whereas in women (aged 68.0 +/- 5.2 y) it was 43.9 +/- 4.3%. Body impedance correlated with fat-free mass (FFM). The best prediction formulas for the FFM from body impedance and anthropometric variables were 1) FFM (kg) = (0.671 x 10(4) x H2/R) + 3.1S + 3.9 where H is body height (m), R is resistance (omega), and S is gender (females, 0; males, 1) (r = 0.94; SEE = 3.1 kg) and 2) FFM (kg) = (0.360 x 10(4) x H2/R) + 0.359BW + 4.5S - 20T + 7.0 where BW is body weight (kg) and T is thigh circumference (m) (r = 0.96; SEE = 2.5 kg). The prediction equations from the literature, generally determined in younger populations, overestimated FFM in elderly subjects by approximately 6 kg and are not applicable to elderly subjects.     

Body composition in 70-year-old adults responds to dietary beta-hydroxy-beta-methylbutyrate similarly to that of young adults.

Studies in young adults have demonstrated that beta-hydroxy-beta-methylbutyrate (HMB) can increase gains in strength and fat-free mass during a progressive resistance-training program. The purpose of this study was to determine whether HMB would similarly benefit 70-y-old adults undergoing a 5 d/wk exercise program. Thirty-one men (n = 15) and women (n = 16) (70 +/- 1 y) were randomly assigned in a double-blind study to receive either capsules containing a placebo or Ca-HMB (3 g/d) for the 8-wk study. Skin fold estimations of body composition as well as computerized tomography (CT) and dual X-ray absorptiometry (DXA) scans were measured before the study and immediately after the 8-wk training program. HMB supplementation tended to increase fat-free mass gain (HMB, 0.8 +/- 0.4 kg; placebo, -0.2 +/- 0.3 kg; treatment x time, P = 0.08). Furthermore, HMB supplementation increased the percentage of body fat loss (skin fold: HMB, -0.66 +/- 0.23%; placebo, -0.03 +/- 0.21%; P = 0.05) compared with the placebo group. CT scans also indicated a greater decrease in the percentage of body fat with HMB supplementation (P < 0.05). In conclusion, changes in body composition can be accomplished in 70-y-old adults participating in a strength training program, as previously demonstrated in young adults, when HMB is supplemented daily.     

Comparison of methods for assessing body-composition changes over 1 y in postmenopausal women

BACKGROUND: Advances in dual-energy X-ray absorptiometry (DXA) software algorithms have improved the accuracy of this method for body-composition measurement. OBJECTIVE: Our objective was to compare the utility of DXA, underwater weighing (UWW), and a multicomponent model (MC) for assessing changes in body composition. DESIGN:: Previously sedentary women aged 40-66 y were randomly assigned to exercise training (ET; n = 36) and no exercise training (NT; n = 40). ET subjects exercised 3 d/wk; NT subjects remained sedentary. Changes in body mass, fat mass, and fat-free mass over 1 y were assessed by the 3 methods. RESULTS: Correlations among methods were significant and large (0.73-0.97). Body weight did not change significantly in either group. In the ET group, fat-free mass increased significantly as assessed by DXA (0.7 +/- 1.0 kg) but changes assessed by MC and UWW were not significant. Changes in fat mass and percentage body fat in the ET group were not significant. SDs for changes in fat mass and percentage body fat, respectively, from DXA were 2.5 kg and 2.7%; for MC, 5.5 kg and 7.1%; and for UWW, 4.4 kg and 5.8%. In the NT group, changes in fat-free mass, fat mass, and percentage body fat were significant (P 相似文献   

有氧联合抗阻运动对中度智力障碍青少年干预效果评价

  目的  探讨有氧联合抗阻运动对中度智力障碍青少年的干预效果,为促进特殊人群健康成长提供参考。  方法  选取佛山市顺德区启智中学29名12~17岁中度智力障碍青少年,使用随机数字表分为干预组(16名)和对照组(13名),干预组进行为期11周的有氧联合抗阻运动,对照组保持原有活动。比较两组受试者干预前后身体成分、肌肉力量、心肺耐力、平衡能力的变化。  结果  干预后干预组骨骼肌(22.90±3.63)kg、肌肉量(39.75±5.57)kg、去脂体重(41.52±6.79)kg、坐式手臂支撑(49.19±35.28)s、站立计时测试(22.13±6.01)s、半仰卧起坐(20.12±6.48)个、握力、2 min踏步运动后即刻心率(91.43±13.44)次/min、闭眼单脚站立与运动前相比显著提高,体脂肪下降(t值分别为2.57, 2.72, 2.07, 2.10, 3.31, 2.92, 2.76, 3.44, 2.86, 2.04, 2.38, -2.92,P值均＜0.05);干预后组间相比,坐式手臂支撑、闭眼单脚站立(右)提高,差异均有统计学意义(P值均＜0.05)。  结论  有氧联合抗阻运动有助于提高中度智力障碍青少年的肌肉力量和耐力、心肺耐力和平衡能力。     

Effects of equal weight loss with orlistat and placebo on body fat and serum fatty acid composition and insulin resistance in obese women

BACKGROUND: Dietary fat has been reported to influence insulin sensitivity. OBJECTIVE: The objective of the study was to determine how identical weight loss (target: loss of 8% of body weight over 3-6 mo) in women taking orlistat or placebo combined with a hypocaloric diet influences body composition and insulin sensitivity. DESIGN: Forty-seven obese women [body mass index (in kg/m(2)): 32.1 +/- 0.4] were randomly assigned to receive either orlistat (120 mg 3 times daily; n = 23) or placebo (n = 24) with a hypocaloric diet. Whole-body insulin sensitivity (insulin clamp technique), serum fatty acids, and body composition (magnetic resonance imaging) were measured before and after weight loss. RESULTS: The groups did not differ significantly at baseline with respect to age, body weight, intraabdominal and subcutaneous fat volumes, or insulin sensitivity. Weight loss did not differ significantly between the orlistat (7.3 +/- 0.2 kg, or 8.3 +/- 0.1%) and placebo (7.4 +/- 0.2 kg, or 8.2 +/- 0.1%) groups. Insulin sensitivity improved significantly (P < 0.001) and similarly after weight loss in the orlistat (from 4.0 +/- 0.3 to 5.1 +/- 0.3 mg x kg fat-free mass(-1) x min(-1)) and placebo (from 4.4 +/- 0.4 to 5.4 +/- 0.4 mg x kg fat-free mass(-1) x min(-1)) groups. Intraabdominal fat and subcutaneous fat decreased significantly in both groups, but the ratio of the 2 decreased significantly only in the orlistat group. The proportion of dihomo-gamma-linolenic acid (20:3n-6) in serum phospholipids was inversely related to insulin sensitivity both before (r = -0.48, P < 0.001) and after (r = -0.46, P < 0.001) weight loss, but it did not change significantly in either group. CONCLUSIONS: Weight loss rather than inhibition of fat absorption enhances insulin sensitivity. A decrease in fat absorption by orlistat appears to favorably influence the ratio between intraabdominal and subcutaneous fat, which suggests that exogenous fat or its composition influences fat distribution.     

Effects of weight loss on substrate oxidation, energy expenditure, and insulin sensitivity in obese individuals.

To evaluate the effect of weight loss on substrate oxidation, energy expenditure, and insulin sensitivity we studied 12 obese subjects (body mass index 33.4 +/- 1.1) before and after 6 wk of a very-low-calorie diet (VLCD) with euglycemic insulin clamp in combination with indirect calorimetry. Body weight decreased from 105.3 +/- 4.6 to 94.1 +/- 4.0 kg (P less than 0.001) and fat mass from 47.2 +/- 3.6 to 37.7 +/- 3.0 kg (P less than 0.001). Total glucose disposal during insulin clamp increased from 30.4 +/- 4.3 to 38.4 +/- 4.4 mumol.kg lean body mass (LBM)-1.min-1 (P less than 0.05), insulin-stimulated glucose oxidation from 14.3 +/- 4.6 to 19.1 +/- 1.4 mumol.kg LBM-1.min-1 (P less than 0.05), and non-oxidative glucose metabolism from 16.0 +/- 3.8 to 19.3 +/- 3.6 mumol.kg LBM-1.min-1 (NS). Lipid oxidation decreased in the basal state (P less than 0.05) and during the insulin clamp (P less than 0.01). The basal rate of energy expenditure decreased from 99.1 +/- 4.6 to 88.5 +/- 2.7 kJ.kg LBM-1.min-1 (P less than 0.05) after weight reduction. A reduction in fat mass achieved by VLCD is associated with reduced lipid oxidation and, because of substrate competition, enhanced glucose oxidation. The physiological consequence is improved insulin sensitivity.     

Effects of familial predisposition to obesity on energy expenditure in multiethnic prepubertal girls

BACKGROUND: The prevalence of childhood obesity is increasing and the causes of this are unknown. OBJECTIVE: The objective of this study was to determine whether energy expenditure (EE), measured by 24-h calorimetry and doubly labeled water, differed in normal-weight-for-height, multiethnic prepubertal girls with or without a familial predisposition to obesity. DESIGN: Normal-weight, prepubertal white (n = 52), African American (n = 30), and Hispanic (n = 19) girls with a mean (+/-SD) age of 8.5 +/- 0.4 y were studied according to parental leanness and overweight or obesity. The girls were grouped according to whether they had 2 lean parents (n = 30), 2 obese parents (n = 27), or 1 lean and 1 obese parent (n = 44). Basal metabolic rate (BMR), sleeping metabolic rate (SMR), 24-h EE, respiratory quotient, heart rate, and activity were measured by 24-h room calorimetry; free-living total EE (TEE), activity-related EE (AEE), and physical activity level were measured by doubly labeled water. EE was standardized by fat-free mass (FFM). RESULTS: There were no significant differences among familial groups in weight, height, fat mass, FFM, or percentage body fat. African American girls had a higher FFM than did white or Hispanic girls (P < 0.05). BMR, SMR, 24-h EE, respiratory quotient, heart rate, and activity levels were not significantly different among familial groups. Additionally, there were no significant familial group differences in TEE, AEE, or physical activity level. However, BMR, SMR, and TEE were lower in African American girls than in white girls (P < 0.05). CONCLUSION: There was no significant difference in EE between normal-weight, multiethnic prepubertal girls predisposed to obesity and those not predisposed to obesity.     

Endurance capacity and high-intensity exercise performance responses to a high fat diet

The effects of adaptation to a high-fat diet on endurance performance are equivocal, and there is little data regarding the effects on high-intensity exercise performance. This study examined the effects of a high-fat/moderate protein diet on submaximal, maximal, and supramaximal performance. Twenty non-highly trained men were assigned to either a high-fat/moderate protein (HFMP; 61% fat diet) (n = 12) or a control (C; 25% fat) group (n = 8). A maximal oxygen consumption test, two 30-s Wingate anaerobic tests, and a 45-min timed ride were performed before and after 6 weeks of diet and training. Body mass decreased significantly (-2.2 kg; p < or = .05) in HFMP subjects. Maximal oxygen consumption significantly decreased in the HFMP group (3.5 +/- 0.14 to 3.27 +/- 0.09 L x min(-1)) but was unaffected when corrected for body mass. Perceived exertion was significantly higher during this test in the HFMP group. Main time effects indicated that peak and mean power decreased significantly during bout 1 of the Wingate sprints in the HFMP (-10 and -20%, respectively) group but not the C (-8 and -16%, respectively) group. Only peak power was lower during bout 1 in the HFMP group when corrected for body mass. Despite significantly reduced RER values in the HFMP group during the 45-min cycling bout, work output was significantly decreased (-18%). Adaptation to a 6-week HFMP diet in non-highly trained men resulted in increased fat oxidation during exercise and small decrements in peak power output and endurance performance. These deleterious effects on exercise performance may be accounted for in part by a reduction in body mass and/or increased ratings of perceived exertion.