Changes in energy expenditure and substrate oxidation resulting from weight loss in obese men and women: is there an important contribution of leptin?

The aim of the present study was to determine the impact of weight loss and its related metabolic and hormonal changes on resting energy expenditure (REE) and substrate oxidation. Forty subjects (16 men and 24 women) took part in a 15-week weight loss program that consisted of drug therapy (fenfluramine, 60 mg/day) or placebo coupled to an energy restriction (-700 Cal/day). Subjects were asked to come to the laboratory after an overnight fast for an indirect calorimetry measurement before and after weight loss. Fasting blood samples were also drawn and were analyzed for plasma glucose, insulin, leptin, and free fatty acid determinations. This program reduced body weight by 11% and 9% (P < 0.01) in men and women, respectively. Fat mass (FM) and fat-free mass (FFM) were also significantly reduced in both sexes. A significant decrease in REE (13%; P < 0.01) and fat oxidation (11%; P = 0.08) was observed in men in response to this program, whereas no significant differences were noted for these variables in women. In men, positive correlations were found between changes in FFM and energy-related variables, whereas the best predictor of changes in REE and substrate oxidation was the change in FM in women. The most important finding of this study is that in men, the association between changes in fasting plasma leptin and changes in REE (r = 0.50; P < 0.01) and fat oxidation (r = 0.63; P < 0.01) persist after correction for changes in body composition. These results suggest that a comparable weight loss is accompanied by a greater decrease in REE and substrate oxidation in men than in women, and that these changes are better explained by changes in leptinemia in men and by changes in FM in women.     

The fat-free mass compartment influences serum leptin in men

OBJECTIVE: Recent experimental work in mice has demonstrated that leptin is synthesized by muscle cells. As this latter tissue is the main target for insulin-estimulated glucose disposal, we hypothesized that the muscular and fat-free mass (FFM) compartments might influence serum leptin levels in humans through increased insulin resistance. DESIGN AND METHODS: We evaluated body composition (through bioelectric impedance and anthropometrical parameters), insulin resistance (using the fasting insulin resistance index (FIRI) and insulin sensitivity (S(I)) from the minimal model analysis) and leptin levels in 140 men and 114 women. RESULTS: Serum insulin, FIRI and leptin levels were significantly increased in men in the highest quintile of FFM. Leptin levels positively correlated with FFM in men (r=0.24, P=0004) but not in women (r=0.02, P=not significant). With weight gain, however, approximately 25% of the additional weight is lean mass, so that obese people have higher fat-free mass than lean people. Hence, we performed a multiple linear regression analysis in a stepwise manner to predict leptin levels, in which fat mass (FM), FFM, and FIRI, but not age or waist-to-hip ratio (WHR) independently contributed to 32%, 6% and 3% of the variance in serum leptin levels in men. In women, FM (49%), FIRI (3.6%) and WHR (2.4%), but not FFM or age explained this variance. In a sample of 40 subjects, S(I) and leptin correlated with mid-arm muscle circumference (r=-0.51, P=0.03 and r=0.53, P=0.02) and mid-arm muscle area (r=-0.52, P=0.03 and r=0.53, P=0.02) in men (n=17) but not in women (n=23). CONCLUSIONS: The fat-free mass compartment contributes to the variability of serum leptin levels in men. Whether insulin resistance at this level mediates an increased production of leptin merits further research.     

Influence of fat-free mass and functional status on resting energy expenditure in underweight elders

BACKGROUND: In underweight elders, resting energy expenditure (REE) and its relationship with fat-free mass (FFM) could be modified by sarcopenia, physical activity, and functional limitation. The aims of this study were to investigate REE and its relationship with quantity and metabolic activity of FFM and to evaluate the influence of functional status on REE in underweight elderly subjects. METHODS: Forty-eight underweight elders (BMI < 20) and 54 normal weight elderly subjects (BMI 20-30) as a control group were selected. Body composition was determined by dual energy x-ray absorptiometry (DEXA). REE was measured by indirect calorimetry. Ability in activities of daily living (ADLs) was assessed by the Katz index. RESULTS: Underweight elders had significantly lower FFM, FFM index (FFM/height(2)), and REE than healthy subjects. REE adjusted for FFM with analysis of covariance remained significantly lower in the underweight group (1287 +/- 85 vs 1715 +/- 139 kcal/day in men, and 1124 +/- 63 vs 1366 +/- 91 kcal/day in women). Katz index in the underweight group was inversely correlated with REE (r = -0.68; p <.001) even after removal of FFM, FM, and gender, by multiple regression analysis. In this model, FFM and Katz index together explained approximately 54% of REE variability. CONCLUSIONS: Underweight elderly subjects show a hypometabolism due to a reduction of both FFM quantity and its metabolic activity. Functional status in ADLs comes out as an important predictor of REE independently from FFM. The limited physical activity might be the underlying determinant of this hypometabolism, but further investigations are necessary to confirm this issue.     

Plasma leptin concentrations, basal metabolic rates and respiratory quotients in young and older adults

OBJECTIVE: To-examine the interrelationship of circulating leptin concentrations, basal metabolic rates (BMR) and respiratory quotients (RQ) in young and older adults. DESIGN: Cross sectional study. SUBJECTS: Seventy-six Australian men and women, 48 young (< 35 y) and 28 older ( > or = 50 y). MEASUREMENTS: Fasting plasma leptin concentrations by RIA, BMR and RQ by indirect calorimetry, percentage body fat (BF%), fat mass (FM) and fat-free mass (FFM) from total body water (TBW) based on deuterium dilution, waist and hip circumferences from anthropometry. RESULTS: Older subjects had significantly higher BF%, FM and waist-to-hip ratio (WHR), but significantly lower FFM and absolute BMR as compared to younger subjects. Absolute leptin concentrations were 60% higher in older subjects but did not achieve statistical significance. There was, however, a significant gender x age group interaction in leptin concentrations. This was reflected in a significant inverse relationship between age group and leptin in women when data was controlled for waist circumference (r = -0.38, P = 0.028), or FM (r = -0.36, P = 0.042). A similar relationship was not observed in men on controlling for BF% or FM. Log transformed plasma leptin was best explained by a model that included BF%, gender, age-group, gender x age-group and WHR r = 0.75, adjusted r2 = 0.56, standard error of estimate (SEE) = 0.73 ng/ml). BMR was best explained by FFM, FM and age group r = 0.94, adjusted r2 = 0.87; SEE = 429 kJ/day). On controlling for BF%, WHR and FFM, leptin was negatively related to RQ only in older men (r = -0.67, P = 0.033). There was no relationship of leptin to BMR in the groups studied. CONCLUSION: The study demonstrates an age-related modification of the gender bias in leptin, and a gender-specific inverse relationship between leptin and RQ in older people. The decline in leptin and the lack of a relationship between RQ and leptin in older women may indicate an increased risk of weight gain relative to older men.     

Gender difference in the effect of body composition on energy metabolism

OBJECTIVE: The aim of this study was to investigate the relationship between energy expenditure (EE) and fat mass (FM) by using a cross-sectional approach to study the linear relationship between body composition variables and EE phenotypes as well as an intervention design to investigate the effect of body weight loss on energy metabolism in both genders. METHODS: The correlations and linear relationships between body weight, FM, fat-free mass (FFM) and abdominal fat vs 24 h EE (EE 24) and sleeping metabolic rate (SMR) were compared between 65 men and 35 women, and before and after weight loss in 10 men and 10 women. RESULTS: Our results showed that for a given FM, men displayed a higher EE than women, independently of FFM. Furthermore, regression analysis revealed that after body weight loss, men displayed a lower SMR for a given FM or FM adjusted for FFM compared to before the treatment, but this was not so in women. However, when FM was adjusted for abdominal fat deposition, the difference between the conditions was no longer observed. CONCLUSIONS: FM has a significant impact on EE only in men. We suggest that abdominal adipose tissue may exert a potent regulatory effect on energy metabolism which would be more detectable in men who generally store more fat in this compartment than women.     

Body composition analysis by leg-to-leg bioelectrical impedance and dual-energy X-ray absorptiometry in non-obese and obese individuals

Aim: The aim of this study is to compare total weight, % body fat (% BF), fat mass (FM) and fat‐free mass (FFM) measured by bioelectrical impedance analysis (BIA) and dual‐energy X–ray absorptiometry (DXA). Methods: This cross‐sectional study included 159 women (mean age: 49.1 ± 10.0 years) and 124 men (mean age: 51.4 ± 8.0 years) subdivided according to sex and body mass index (BMI): BMI < 30 kg/m² (66 women and 50 men); BMI 30–35 kg/m² (53 women and 44 men) and BMI ≥ 35 kg/m² (40 women and 30 men). Bioelectrical impedance was performed in the fasting state on a Tanita TBF‐215 leg‐to‐leg analyser (Tanita, Tokyo, Japan). Whole‐body DXA scans were performed on a Hologic QDR 4500 A bone densitometer (Hologic, Bedford, MA, USA). Total weight, % BF, FM and FFM were tested for intermethod differences. Linear regression and correlation analysis was performed. Limits of agreement and Bland–Altman plots were built. Results: DXA‐derived body composition parameters were not significantly different from BIA estimates and were highly correlated (e.g. for FFM, r = 0.82–0.95). In lean individuals, BIA tended to produce lower values for FM and % BF and higher ones for FFM in comparison with DXA. This trend was reversed at BMI > 35 kg/m². The correlations decreased with increasing BMI. The limits of agreement were much better in men than in women and increased with increasing BMI in both sexes. Conclusions: Compared with DXA, the leg‐to‐leg Tanita TBF‐215 analyser accurately assessed body composition in a heterogeneous group of both sexes. In the very obese women (BMI > 35 kg/m²), BIA measurements should be viewed with caution.     

Testosterone therapy prevents gain in visceral adipose tissue and loss of skeletal muscle in nonobese aging men

BACKGROUND: Trials of testosterone therapy in aging men have demonstrated increases in fat-free mass (FFM) and skeletal muscle and decreases in fat mass (FM) but have not reported the impact of baseline body composition. OBJECTIVE: The objective of the study was to determine the effect, in nonobese aging men with symptoms of androgen deficiency and low-normal serum testosterone levels, of testosterone therapy on total and regional body composition and hormonal and metabolic indices. METHODS: Sixty healthy but symptomatic, nonobese men aged 55 yr or older with total testosterone (TT) levels less than 15 nm were randomized to transdermal testosterone patches or placebo for 52 wk. Body composition, by dual-energy x-ray absorptiometry (FM, FFM, skeletal muscle) and magnetic resonance imaging (abdominal sc and visceral adipose tissue, thigh skeletal muscle, and intermuscular fat) and hormonal and metabolic parameters were measured at wk 0 and 52. RESULTS: Serum TT increased by 30% (P = 0.01), and LH decreased by 50% (P < 0.001). Relative to placebo, total body FFM (P = 0.03) and skeletal muscle (P = 0.008) were increased and thigh skeletal muscle loss was prevented (P = 0.045) with testosterone therapy and visceral fat accumulation decreased (P = 0.001) without change in total body or abdominal sc FM; change in visceral fat was correlated with change in TT levels (r2 = 0.36; P = 0.014). There was a trend to increasing total and low-density lipoprotein cholesterol with placebo. CONCLUSION: Testosterone therapy, relative to placebo, selectively lessened visceral fat accumulation without change in total body FM and increased total body FFM and total body and thigh skeletal muscle mass. Further studies are needed to determine the impact of these body compositional changes on markers of metabolic and cardiovascular risk.     

The effect of gender and body composition method on the apparent decline in lean mass-adjusted resting metabolic rate with age

BACKGROUND: Declining resting energy expenditure (REE) is a hallmark of normal aging, but the cause of this decline remains controversial. Some, but not all, studies have shown that the decline in REE with age is eliminated after adjustment for fat-free mass (FFM). METHODS: We examined the effect of four body composition methods used to assess FFM (underwater weighing [UWW], bioimpedance analysis [BIA], tritium dilution, and total body potassium [TBK]) on the relationship between REE and age in 30 healthy men and 101 healthy women aged 18 to 87 years. RESULTS: The decline in REE with age was significant in women (-80.3 kJ/d/y, p < .004) but not in men (-46.9 kJ/d/y, p = .328). After adjustment for FFM, the decline in REE with age persisted when FFM was measured by BIA, UWW, or tritium dilution, but no decline was seen when TBK was used to adjust for FFM. In both women and men, fat mass was significantly associated with REE after adjusting for age and FFM. CONCLUSION: It is the decline in cell mass with age, detectable by TBK but not by other methods, rather than any metabolic alteration, that explains the decline in FFM-adjusted REE with age.     

Poor prediction of resting energy expenditure in obese women by established equations

The objective of the study was to evaluate the accuracy of established prediction equations that calculate resting energy expenditure (REE) in obese women. This was a cross-sectional study. In 273 mildly to severely obese women (age, 41.7 ± 13.2 years; body mass index, 42.8 ± 7.0 kg/m²), REE was measured by indirect calorimetry (mREE), along with fat mass (FM) and fat-free mass (FFM) by bioelectrical impedance analysis. Eleven established equations were used to predict REE (pREE), with 9 equations basing on the anthropometric parameters body weight and height and 2 equations including body composition parameters (FM, FFM). All equations provided pREE values that significantly correlated with mREE (r > 0.66, P < .001), although 8 equations systematically underestimated mREE (P < .05). Of note, even the best equation was not able to accurately predict mREE with a deviation of less than ±10% in more than 70% of the tested women. Furthermore, equations using body composition data were not superior in predicting REE as compared with equations exclusively including anthropometric variables. Multiple linear regression analyses revealed 2 new equations—one including body weight and age and another including FM, FFM, and age—that explained 56.9% and 57.2%, respectively, of variance in mREE. However, when these 2 new equations were applied to an independent sample of 33 obese women, they also provided an accurate prediction (±10%) of mREE in only 56.7% and 60.6%, respectively, of the women. Data show that an accurate prediction of REE is not feasible using established equations in obese women. Equations that include body composition parameters as assessed by bioelectrical impedance analysis do not increase the accuracy of prediction. Based on our results, we conclude that calculating REE by standard prediction equations does not represent a reliable alternative to indirect calorimetry for the assessment of REE in obese women.     

Total body mass, fat mass, fat-free mass, and skeletal muscle in older people: cross-sectional differences in 60-year-old persons

OBJECTIVES: To evaluate body composition parameters, including fat-free mass (FFM), appendicular skeletal muscle mass (ASMM), relative skeletal muscle mass (RSM) index, body cell mass (BCM), BCM index, total body potassium (TBK), fat mass, percentage fat mass (FM), and their differences between age groups and to evaluate the frequency of sarcopenia in healthy older subjects DESIGN: Cross-sectional, nonrandomized study. SETTING: Outpatient clinic. PARTICIPANTS: Ninety-one healthy men and 100 healthy women age 60 and older. MEASUREMENTS: FFM, ASMM, FM, and percentage fat mass by whole-body dual-energy x-ray absorptiometry; TBK, BCM, and TBK/FFM ratio by whole body potassium-40 counter. RESULTS: All lean body mass parameters were significantly (P <.05) lower in subjects age 80 and older than in those age 70 to 79, except ASMM in women. Mean FFM was 4.2 kg (7.3%) lower in men age 80 and older than in those younger than 70 and 2.9 kg (6.8%) lower in women age 80 and older than in those younger than 70. The skeletal muscle mass, reflected by ASMM, decreased more than FFM. This suggests that nonskeletal muscle mass is proportionally preserved during aging. Forty-five percent of men and 30% of women were sarcopenic by definition of BCM index and 11.0% of men and women by definition of RSM index. CONCLUSIONS: Significant age-related differences exist in body composition of older men and women between age 60 and 95. The greater decrease in TBK and BCM than the decrease in FFM and skeletal muscle mass suggests changing composition of FFM with age. Lack of agreement between two independent sarcopenia indexes suggests that further refinement in the definition of a sarcopenia index is necessary.     

The relationship between body composition and muscle power output in men and women with obesity

In order to investigate the effect of gender, age and level of obesity on body composition and anaerobic power output, and to test the hypothesis that variation in body composition affects muscle power output in obesity, a cohort of 377 subjects (112 males and 265 females, aged 18-75 yr) with different levels of obesity [class IIII, body mass index (BMI) range: 30.6-60.3 kg m(-2)] was cross-sectionally investigated. Body composition was assessed with bioelectric impedance analysis (BIA), in standardized conditions and using obesity-specific prediction formulas. Lower limb anaerobic power output (W) was measured with a modification of the Margaria stair climbing test. In males, a similar increase in fat-free mass (FFM) and fat mass (FM) was observed as a function of BMI, while in females, FM increased more than FFM. In both genders, FFM significantly decreased as a function of age (p<0.001), but was higher in men of all ages. Similar patterns of variation were observed in W. A differently significant correlation between BMI and W was observed between men and women, and it was found by multivariate analysis of variance (MANOVA) that W was affected negatively by age (p<0.001) and positively by BMI (p<0.001) in males, while in females only age had a significant effect (p<0.001) but not BMI. A positive correlation (p<0.001) was detected between FFM and W, in both genders. W per unit body mass, the actual muscle power for rapid external work, was higher in men than in women of all groups, and decreased with age in both genders, but only in older women decreased significantly (p<0.01) depending on BMI. It is concluded that the gender-dependent pattern of variation in body composition may be an important determinant of the different motor limitations observed in men and women. Older women (> or =50 yr) with extreme obesity (class III) suffered from the most serious motor dysfunction within this obese cohort. This result may have important clinical relevance in the care of obesity.     

Resting energy expenditure and body composition in bedridden institutionalized elderly women with advanced-stage pressure sores

BACKGROUND: Our study investigated nutritional status, body composition, and resting energy expenditure (REE) in elderly patients with advanced-stage pressure sores (PS), in addition to researching any hypermetabolic condition and its relationship with PS size. METHODS: The study involved 52 institutionalized bedridden elderly women (aged 83.7 +/- 6.3 years), divided into two groups: 23 with advanced-stage (stage 3 and 4) PS and 29 without PS. Albumin, prealbumin, and retinol-binding protein were measured in all patients, and fat-free mass (FFM) and fat mass (FM) were obtained by dual-energy x-ray absorptiometry (DEXA). REE was measured by indirect calorimetry and predicted with the Harris-Benedict formula. PS area and volume were also measured. RESULTS: The elderly women with and without PS were comparable in age, FFM, and FM. Mean albumin, prealbumin, and retinol-binding protein values were lower in cases with PS. Unadjusted mean REE was significantly higher in patients with PS (1212.3 +/- 236.7 vs 1085.5 +/- 161.3 kcal/d; p <.05), even after adjusting for FFM or expressed per kilogram of body weight (25.8 +/- 6.7 vs 21.1 +/- 4.0 kcal/d/kg; p <.01). Hypermetabolism, i.e., a measured REE > 110% of the predicted REE, was seen in 74% of patients with PS and 38% of controls. The difference between measured and predicted REE (DeltaREE) correlated with PS volume (r = 0.58; p <.01), but not with area. CONCLUSION: Advanced-stage PS in elderly women are associated with a hypermetabolic state that is influenced by the volume of the PS.     

Longitudinal body composition changes in old men and women: interrelationships with worsening disability

BACKGROUND: Few studies have evaluated prospectively age-related body composition changes and their relationships with worsening disability in the elderly population. METHODS: Ninety-seven women and 62 men aged 71.4+/-2.2 and 71.6+/-2.2 years, respectively, at baseline underwent dual-energy x-ray absorptiometry determinations at baseline and at 2- and 5.5-year follow-up intervals to measure total body and leg fat (FM) and total, appendicular, and leg fat-free mass (FFM). Height, weight, body mass index (BMI), and waist circumference (as well as reported disabilities using a four-level scale) were evaluated at baseline and at 2- and 5.5-year follow-up. RESULTS: In both sexes, total FM did not change significantly, while total, appendicular, and leg FFM significantly decreased over the study follow-up. In men and women losing weight, BMI, total and leg FM, and total, appendicular, and leg FFM significantly decreased. In weight-stable men and women, appendicular and leg FFM significantly decreased and BMI, waist circumference, and total FM significantly increased. Men lost significantly more total, appendicular, and leg FFM than did women, irrespective of whether they maintained or lost weight. Over the follow-up period, 43.3% of women and 43.5% of men declined in one or more levels of reported disability. We evaluated the effect of age, baseline BMI, FM, FFM, number of diseases, baseline 6-minute walking test, categories of weight change, total, appendicular, or leg FFM changes, total FM and waist changes on the probability of a decline in one or more levels of reported disability score over the follow-up period, taking into account sex. Patients losing appendicular and leg FFM were 2.15 and 2.53 times, respectively, more likely to report increased disability than were patients without FFM loss. CONCLUSIONS: Reduction in appendicular or leg FFM was the main predictor of decline in one or more levels of reported disability in older men and women, and accounted for about a 2-fold increase in risk.     

Resting metabolic rate, body composition, and serum leptin concentrations in a free-living elderly population

OBJECTIVE: The present study investigated the relationship between serum leptin concentrations and resting metabolic rate (RMR) in a large study group of elderly individuals with special consideration of body composition and body fat distribution as possible confounders. DESIGN AND METHODS: The subjects were 122 women (age: 69+/-6 years, body mass index (BMI): 26.3+/-3.6 kg/m(2)) and 82 men (age: 69+/-5 years, BMI: 26.0+/-2.6 kg/m(2)). RMR was measured by indirect calorimetry and body composition by the bioelectrical impedance method. Serum leptin levels were determined by radioimmunoassay. RESULTS: There was a strong correlation between fat mass (FM) and serum leptin levels in both sexes. An age-related decline in leptin levels adjusted for FM was observed only in the women. After adjustment of RMR for both fat-free mass (FFM) and FM, leptin levels were not associated with RMR. In stepwise multiple regression analysis, FFM was the main predictor of RMR, explaining 35.8% and 47.6% of the variance of RMR in men and women respectively. FM did not explain variance in RMR in men, but accounted for 2.6% of the variance in RMR in women. Waist-hip-ratio and age influenced RMR only in males, explaining 5.7% and 4.0% of the variance in RMR respectively. CONCLUSION: Leptin is not a significant predictor of RMR in the elderly, but body composition and distribution of body fat are significantly associated with RMR.     

L-tri-iodothyronine is a major determinant of resting energy expenditure in underweight patients with anorexia nervosa and during weight gain

OBJECTIVE: We aimed to define the effect of L-3,5,3'-tri-iodothyronine (T(3)) on metabolic adaptation in underweight patients with anorexia nervosa (AN) as well as during weight gain. METHODS: This involved clinical investigation of 28 underweight patients with AN, who were compared with 49 normal-weight controls. A subgroup of 17 patients was followed during weight gain. Resting energy expenditure was measured by indirect calorimetry. Body composition was measured by anthropometry as well as bioelectrical impedance analysis. Energy intake (EI) was assessed by a 3-day dietary record. Plasma concentrations of thyroid hormones (thyroxine (T(4)), T(3) and thyrotropin (TSH)) were analyzed by enzyme immunoassays. RESULTS: When compared with normal-weight women, underweight patients with AN had reduced fat mass (FM) (-71.3%), fat-free mass (FFM) (-13.1%), resting energy expenditure (REE) (-21.8%), T(3)- (-33.4%) and T(4)-concentrations (-19.8%) at unchanged TSH. REE remained reduced after adjustment for FFM (-24.6%). T(3) showed a close association with REE. This association remained after adjustment of REE for FFM. Treatment of underweight AN patients resulted in a mean weight gain of 8.3 kg. This was mainly explained by an increase in FM with small or no changes in FFM. REE and T(3) also increased (+9.3% and +33.3% respectively) at unchanged TSH and T(4). There was a highly significant association between weight gain-induced changes in T(3) and changes in adjusted REE (r = 0.78, P < 0.001, based on Pearson's correlation). An increase in plasma T(3) concentrations of 1.8 pmol/l could explain an increase in REE of 0.6 MJ/day (that is, a 32% increase in T(3) was associated with a 13% increase in REE). CONCLUSIONS: Our data provide evidence that the low T(3) concentrations add to metabolic adaptation in underweight patients with AN. During weight gain, increases in T(3) are associated with increases in REE, which is independent of FFM. Both results are evidence for a physiologic role of T(3) in modulation of energy expenditure in humans.     

Serum leptin and body composition in children with familial GH deficiency (GHD) due to a mutation in the growth hormone-releasing hormone (GHRH) receptor

OBJECTIVE: The relationship between GH, body composition and leptin in children remains ill-defined. We have therefore examined the impact of severe GH deficiency (GHD) due to a mutation in the GHRH receptor on serum leptin concentrations and body composition in childhood. PATIENTS: 12 affected children and young people (GHD) (4 M:8F, age 5.4-20.1 years, 8 Tanner stage (TS) 1-2, 4 TS 3-5) and 40 healthy controls (C) from the same region (13 M:27F, age 5.3-18.4 years, 20 TS 1-2, 20 TS 3-5). METHODS: Percent body fat was determined by infra-red interactance, from which the amounts of fat mass (FM, kg) and fat free mass (FFM, kg) were derived. Serum leptin concentrations were measured in a single fasted, morning serum sample and results expressed as a concentration and as leptin per unit fat mass (L/FM, ng/ml/kg). To control for differences in sex and pubertal maturation, leptin standard deviation scores (leptin SDS) were calculated using normative data from UK children. RESULTS: FFM was significantly lower in GHD children than in controls (TS 1-2 P < 0.05, TS 3-5 P < 0.001). FM did not differ significantly between the two groups. Serum leptin concentrations, leptin per unit fat mass and leptin SDS were significantly elevated in GHD children both peripubertal and pubertal compared with controls. Using all subjects, stepwise multiple linear regression with FM, FFM, age, puberty and sex as explanatory variables and leptin concentration as the dependent variable indicated that 59% of the variability in leptin could be accounted for by FM (+, 45%), FFM (-, 9%) and sex (+, 5%) (P < 0.001). However on inclusion of GH deficiency (coded GHD = 1, control = 2) as an explanatory variable 73% of the variability in leptin was explained by FM (+, 45%), GHD (-, 22%) and sex (+, 6%) (P < 0.001). CONCLUSIONS: These data indicate that severe GH deficiency in children is associated with elevated leptin concentrations, irrespective of sex or pubertal stage. This increase is not associated with differences in fat mass but is related to reduced fat free mass in GH deficiency. Furthermore in this population there may be an additional effect of GH deficiency on leptin, independent of the influences of sex and body composition.     

Skeletal muscle low attenuation area and maximal fat oxidation rate during submaximal exercise in male obese individuals.

BACKGROUND: Muscle triacylglycerols (TG) are known to be a source of energy during submaximal exercise. OBJECTIVE: The aim of this study was to assess whether an index of muscle fat content is related to maximal fat oxidation rate (FATOXmax) in 58 obese men (mean age 46.0+/-0.8 (s.e.) y, body weight 96.4+/-1.4 kg, percentage fat: 31.9+/-0.5%) [corrected]. DESIGN: FATOXmax was defined as the highest value of fat oxidation rate, measured by indirect calorimetry, while walking on a treadmill (4.3 km/h) at three different slopes: 0% (40+/-1% of VO2max), 3% (47+/-1% of VO2max) and 6% (58+/-1% of VO2max). Fat-free mass (FFM) and fat mass (FM) were measured with the underwater technique and scans were obtained by computed tomography (CT) at the mid thigh level to assess areas of adipose tissue within skeletal muscle, ie deep adipose tissue (DAT), subcutaneous adipose tissue (SAT), skeletal muscle (M) and low attenuation skeletal muscle (LAM, range of attenuation values: 0-34 Hounsfield units). LAM and DAT were used as indices of skeletal muscle fat content. RESULTS: FATOXmax, adjusted for age, was correlated with FFM (r=0.26, P<0.05), LAM (r=0.29, P<0.05), abdominal visceral adipose tissue (r=0.30, P<0.05) and plasma free fatty acid (FFA) levels (r=0.33, P<0.05) but not with SAT (r=0.03) and DAT (r=0.21) [corrected]. In a stepwise linear multiple regression, plasma FFA, age and LAM significantly predicted FATOXmax (r2=0.27). Each independent variable explained about 9% of the FATOXmax variance. CONCLUSION: LAM makes a significant but weak contribution to the modulation of fat oxidation during submaximal exercise in obese men.     

Characterization of the metabolic phenotypes of Cushing's syndrome and growth hormone deficiency: a study of body composition and energy metabolism

OBJECTIVE: A comparison of the severity and distribution of perturbations in body composition and their relationship to energy metabolism in glucocorticoid excess and GH deficiency (GHD) has not been undertaken before. The aim of this study was to investigate the impact of Cushing's syndrome (CS) and GHD on whole and regional body composition and energy metabolism. DESIGN: Cross-sectional study design. PATIENTS: Eighteen subjects with CS (12 women, aged = 41.5 +/- 3.0 years, 24-h urinary free cortisol = 1601 +/- 361 nmol/day, normal < 300 nmol/day), 22 subjects with GHD (14 women, age = 42.9 +/- 2.9 years) and 18 normal subjects (11 women, age = 46.8 +/- 2.8 years). MEASUREMENTS: Lean body mass (LBM), fat mass (FM) and regional body composition were assessed by dual-energy X-ray absorptiometry (DEXA). Resting energy expenditure (REE) and fat oxidation (Fox) were assessed by indirect calorimetry. RESULTS: Mean percentage FM was significantly greater by 30% in CS (P = 0.002) and 22% in GH-deficient subjects (P = 0.014) than in normal subjects. LBM was significantly lower by 15% in CS (P = 0.002) and 11% in GHD (P = 0.013). In CS, the proportion of lean tissue in the limbs was 12% less than in normal (P = 0.001) and GH-deficient subjects (P = 0.0005). Truncal fat represented a greater proportion of total FM in CS (52.5 +/- 1.8%vs. 46.9 +/- 1.3%, P = 0.014) than in normal subjects, but not in GHD. REE and Fox, corrected for LBM, were significantly lower in GHD (P < 0.02 for both vs. normal) but not in CS. CONCLUSION: FM was higher and LBM lower in both CS and GHD. However, there is a greater abnormality of regional body composition in patients with CS who exhibit a lower limb lean mass and a greater truncal fat. Reduced REE and Fox contribute to increased adiposity in GHD. As REE and Fox are not perturbed in CS, other mechanisms must explain the marked gain in truncal and total fat.     

Differential effect of resistance training on the body composition and lipoprotein-lipid profile in older men and women

The effects of a 12-week resistance exercise training (RT) program on body composition and serum lipid concentrations were assessed in weight-stable, moderately overweight older men (n = 18) and women (n = 17) aged 54 to 71 years with a body mass index (BMI) of 26 to 36 kg/m2. Following RT, the men had a significant increase in fat-free mass (FFM) and a decrease in percent body fat (%BF) and fat mass (FM), whereas the women demonstrated no change, resulting in significant time-by-sex interactions for FFM (P = .002), %BF (P = .006), and FM (P = .005). There were no changes in total cholesterol (Chol), low-density lipoprotein cholesterol (LDL-C), or triacylglycerol (Tg) due to RT. However, following RT, high-density lipoprotein cholesterol (HDL-C) increased (0.06+/-0.02 mmol/L) in the men and decreased (0.09+/-0.03 mmol/L) in the women (time-by-sex interaction, P = .0004). The Chol/HDL-C ratio decreased (0.36+/-0.11) in the men and increased (0.29+/-0.10) in the women (time-by-sex interaction, P = .0001). For all subjects combined, the changes in HDL-C and the Chol/HDL-C ratio were not related to any changes in body fat stores (ie, %BF or FM), suggesting that RT may potentially alter the lipoprotein-lipid profile in older weight-stable men and women. In conclusion, although the changes in the lipoprotein-lipid profile were small, the men had a significantly increased HDL-C level and decreased Chol/HDL-C ratio, while the women demonstrated opposite changes.