Validation of tetrapolar bioelectrical impedance method to assess human body composition

This study was conducted to validate the relationship between bioelectrical conductance (ht2/R) and densitometrically determined fat-free mass, and to compare the prediction errors of body fatness derived from the tetrapolar impedance method and skinfold thicknesses, relative to hydrodensitometry. One-hundred and fourteen male and female subjects, aged 18-50 yr, with a wide range of fat-free mass (34-96 kg) and percent body fat (4-41%), participated. For males, densitometrically determined fat-free mass was correlated highly (r = 0.979), with fat-free mass predicted from tetrapolar conductance measures using an equation developed for males in a previous study. For females, the correlation between measured fat-free mass and values predicted from the combined (previous and present male data) equation for men also was strong (r = 0.954). The regression coefficients in the male and female regression equations were not significantly different. Relative to hydrodensitometry, the impedance method had a lower predictive error or standard error of the estimates of estimating body fatness than did a standard anthropometric technique (2.7 vs. 3.9%). Therefore this study establishes the validity and reliability of the tetrapolar impedance method for use in assessment of body composition in healthy humans.     

Assessment of nutritional status in rhesus monkeys: comparison of dual-energy X-ray absorptiometry and stable isotope dilution

Body composition estimates from dual-energy X-ray absorptiometry and stable isotope dilution ((2)H and (18)O) were compared in 61 rhesus monkeys (Macaca mulatta) from the ongoing long-term energy restriction study at the University of Wisconsin. Their average age was 18.9 +/- 2.5 y/o. Of the animals, 51% were in the energy restricted group and 38% were females. Although the correlation between methods was highly significant for fat mass (R(2) = 0.97, SEE = 0.25 kg or 7.5%, P < 0.0001) and fat-free mass (R(2) = 0.98, SEE = 0.29 kg or 3.6%, P < 0.0001), we observed that dual-energy X-ray absorptiometry underestimated fat mass by 0.67 +/- 0.26 kg (7.5%, P < 0.0001) and overestimated fat-free mass by 0.57 +/- 0.29 kg (20%, P < 0.0001) when compared with isotope dilution. Taken together with data from the literature, the present results emphasize the usefulness of dual-energy X-ray absorptiometry to derive body composition and thus nutritional status in monkeys, but demonstrate the importance of validation experiments for a given DXA model and software.     

Effects of gender, body composition and birth size on IGF-I in 7- and 8-year-old children

We investigated the relationship between IGF-I, gender, height, weight, body composition and birth size in 260 healthy 7- and 8-year-old children (139 females). All children were born term at Nepean Hospital, Western Sydney. Body composition was measured using dual energy X-ray absorptiometry. IGF-I levels were determined by radioimmunoassay. Girls had higher IGF-I levels than boys (20.2 +/- 6.5 nmol/l compared to 15.9 +/- 6.1 nmol/l, p < 0.001) but there was no correlation between age and IGF-I. IGF-I was positively correlated with height SDS (R(2) = 0.12), weight SDS (R(2) = 0.19), BMI SDS (R(2) = 0.18), total body fat (%) (R(2) = 0.14), and fat-free tissue/cm (R(2) = 0.03). After adjusting for gender and current weight, IGF-I-levels were inversely related to birth size - children with the lowest birth size and heaviest current weight had the highest IGF-I levels. This correlation between birth weight and IGF-I supports the hypothesis that the IGF-I axis is altered in babies who are small for gestational age.     

Body Composition Characteristics During Puberty in Girls and Boys from Eastern Austria

Puberty represents the final stage of sexual differentiation when the individual acquires reproductive capacity. Puberty is not only characterized by maturation of sexual organs and the formation of oocytes and mature spermatozoa, but also by the development of secondary sexual dimorphism. In industrialized countries, the age of puberty has decreased steadily over the last 150 years in association with improved socio-economic conditions. However, the decreased onset of puberty, especially in females, is associated with problematic changes in behaviour such as early onset of sexual activity resulting in high-risk teenage pregnancies. In our study, we analysed the association between body composition (fat tissue and fat-free body mass, estimated by BIA analyses), height, body mass index and fat distribution and signs of puberty such as the timing of menarche in 228 girls and voice breaking and facial hair growth in 191 boys ageing between 10 and 15 years. In both sexes, signs of puberty were associated, highly significantly, with body composition parameters. Nevertheless, marked differences between the two sexes were observed: Female puberty was positively associated with weight status and the absolute and relative amount of body fat, while in males, puberty was positively related with a higher amount of fat-free body mass and a decreased fat mass. Male voice breaking was significantly associated with increased stature, body weight, waist and hip circumference, lean body mass and total body water. In contrast, voice breaking was significantly negatively associated with the fat percentage, the total fat mass and the waist-to-hip ratio. Female menarche was significantly positively associated with increased body weight, weight status, waist and hip circumference and also with increased absolute and relative fat mass, relative hip circumference, lean body mass and total body water. Only the waist-to-hip ratio was significantly negatively associated with the onset of menarche.     

Vital capacity in trained and untrained healthy young adults in the Netherlands

Slow inspiratory vital capacity was measured in 226 healthy young adults, aged from 17 to 35 years. The group included 119 men and 107 women, 87 trained subjects, 71 untrained subjects who intended to take part in a training program for competitive rowing, and 68 untrained subjects who never took part in any competitive sport. The vital capacity increased with height, weight, fat-free mass, height X fat-free mass, and height-independent fat-free mass, with men having significantly higher vital capacities than women of the same height or weight. In both males and females vital capacity showed the best relation with height X fat-free mass (correlation coefficients are 0.78 and 0.57 respectively). Multiple regression on vital capacity with height, weight, fat-free mass, height X fat-free mass, height-independent fat-free mass, percentage body fat, and age increased the correlation coefficient only slightly (0.80 and 0.59 respectively). The subjects had vital capacities that were much higher than those predicted for them by equations originating from the USA. There was no difference between the observed vital capacities and those predicted by equations originating from Europe. There is a difference in vital capacity between the European subjects studied and subjects of similar height studied in the USA. This implies that equations derived from subjects in the USA cannot be applied to European subjects. From our results we conclude that vital capacity is not increased by physical activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of physical activity and dietary restraint on resting energy expenditure in young nonobese females

An understanding of the physiological and behavioral determinants of resting energy requirements is important to nutritional considerations in females. We examined the influence of endurance training and self-reported dietary restraint on resting metabolic rate and fasting plasma hormones in 44 nonobese females characterized for body composition, maximal aerobic power (VO2 max), and daily energy intake. To examine the association of metabolic rate and dietary restraint with hormonal status, fasting plasma levels of insulin, glucose, and thyroid hormones (total and free fractions of thyroxine and triiodothyronine) were determined. In univariate analysis, resting metabolic rate (kcal.min-1) was positively related to VO2 max (L.min-1) (r = 0.54; p less than 0.01). This relationship, however, was partially dependent on body size, since fat-free mass was also related to resting metabolic rate (r = 0.42; p less than 0.01) and VO2 max (L.min-1) (r = 0.75; p less than 0.01). After controlling for fat-free weight using partial correlation analysis, the relation between RMR and VO2 max was weaker but controlling for fat-free weight using partial correlation analysis, the relation between RMR and VO2 max was weaker but still significant (partial r = 0.38; p less than 0.05). On the other hand, high levels of dietary restraint were associated with higher levels of body fat (r = 0.31; p less than 0.05) and a lower resting metabolic rate (r = -0.29; p = 0.07). These associations persisted after control for differences in fat-free mass. Total energy intake as well as total and free levels of triiodothyronine were not related to resting metabolic rate or level of dietary restraint.(ABSTRACT TRUNCATED AT 250 WORDS)     

Blood serum concentration of lipids and lipoproteins and body composition

The purpose of this study is the analysis of the relationship of blood serum apolipoprotein E (apoE), total cholesterol (TC), triglycerides (TG) and high-density and low-density lipoproteins (HDL, LDL), with body mass index (BMI), relative body surface area (RBSA) and body muscle (BM) and body fat (BF). The subjects are males and females aged 14-16 (adolescent age group 1: n1M = 141, n1F = 151) and 18-25 (young adult group 2, n2M = 16, n2F = 46). Significant correlations of serum TG and HDL with somatometric indicators were not observed. In the female samples, TC content directly correlates (p < 0.05) with BF (r1 = 0.164; r2 = 0.418) and negatively correlates with BM (r1 = -0.165; r2 = -0.352). The blood serum concentration of apoE is significantly correlated with body composition in adolescent females (for BF r1 = -0.168; for BM r1 = 0.266; p < 0.05); in males 14-16 years old, the both correlations have a significance level p < 0.06. In young adult females TC and LDL content negatively correlates with RBSA (r2 = -0.386 and -0.377 respectively; p < 0.05) and positively correlates with BMI (r2 = 0.413 and 0.415 respectively; p < 0.05). Adolescent females and young adult females have opposite relationships between FC and apoE concentration. In females 14-15 years old apoE concentration decreases as FC increases. In females 16-17 the correlation disappears, and in older females apoE concentration and FC increase together.     

Kinetics of stable isotope and body composition in olive baboons (Papio anubis) estimated by deuterium dilution space: a pilot study

Morphometrics and isotope-labelled water were used to determine body composition [total body water, total body fat and fat-free mass (FFM)] of three captive female olive baboons (Papio anubis). Mean mass was 16.5 kg, comparable with other captive settings but heavier than wild olive baboons. Average water content was 66%; FFM averaged 90.5%. Baboon females have less body fat than human counterparts. Compared with captive or wild baboons, these females were adequately nourished for their energy expenditure. A positive association between total mass and FFM existed, but due to the small sample no general relationship was observed for body fat or FFM and condition or size measures. The kinetics of deuterium equilibration in body fluids for baboons was determined as 3-4 hours after injection, similar to that for humans. Deuterium dilution technique appears to be an appropriate method for studying body composition in baboons, although a larger sample is needed for relationships between morphometric indices and body composition.     

Relationships between body fat measured by DXA and subcutaneous adipose tissue thickness measured by Lipometer in adults

The aim of this study was to examine the relationships between body fat measured by DXA and subcutaneous adipose tissue layers (SAT-layers) measured by LIPOMETER in adult males (n=28) and females (n=53). Body height and mass were measured and BMI was calculated (kg/m2). Measurements of the thicknesses of SAT-layers by LIPOMETER were performed at 15 original body sites. Body composition was measured using DXA. Total body fat % measured by DXA was highly dependent on the SAT-layers in the upper back and inner thigh in males (87.1%, R(2)x100) and the lateral chest, biceps, and calf in females (78.5%, R(2)x100). There were gender differences in trunk fat mass and right hand and leg fat mass calculation using specific SAT-layers. In conclusion, our results indicate that there are close relationships between SAT-layers and body fat measured by DXA. However, there are big differences between genders.     

Improved growth of lipoprotein lipase deficient kittens by feeding a low-fat, highly digestible diet small star, filled

Adult domestic cats homozygous with a naturally occurring Gly412Arg LPL gene mutation are good models for the study of LPL deficiency. Previous studies report that homozygous LPL deficient kittens have reduced growth rates and develop subnormal body fat mass. It was hypothesized in the present study that homozygote kittens would have normal growth if provided a standard low fat, highly digestible diet at weaning and that their body fat would be increased by provision of a diet high in protein. When fed a nutritionally complete, 10% fat, purified or commercial extruded diet, the body weights of homozygous (n = 24), heterozygous (n = 25) and normal (n = 16) kittens were determined at birth, 2, 3, 4, 6, 12 and 18 weeks of age. Male homozygote kittens from homozygote dams had reduced weight gains (p < 0.05) compared to normal males at 2, 3 and 4 weeks. Female heterozygotes and homozygotes from homozygote and heterozygote dams had reduced weight gains (p < 0.05) compared to normal females at 2, 3, 4 and 6 weeks. By 6 weeks for males and 18 weeks for females, genotype related differences in weight gain were not observed. At 30 weeks, homozygotes and heterozygotes were given either a 60 or 30% (dry matter) protein diet for two months. As indicated by deuterium dilution estimation of body composition, cats eating the 30% protein diet (n = 12) tended to have a lower increase in lean body mass (p = 0.057) and a greater increase in fat mass (p = 0.092) compared to cats eating the 60% protein diet (n = 12). Increase in lean body mass among homozygotes tended to be not as great as that observed in heterozygotes (p = 0.057). Poor postweaning gains previously reported in homozygotes probably reflected inappropriate selection of diet for this genotype. The high protein diet increased the rate of lean body mass development but not body fat mass.     

Leptin concentrations and their relation to body fat distribution and weight loss--a prospective study in individuals with impaired glucose tolerance. DPS-study group.

Leptin is proposed to be involved in regulation of body weight. Only little information is available on leptin concentrations in individuals with impaired glucose tolerance (IGT). The aim of the present study was to assess the effect of body fat distribution and weight reduction on serum leptin levels in a prospective setting in IGT subjects. Sixty-nine individuals with impaired glucose tolerance aged 45-64 years participated in this prospective study. Serum leptin levels were about 300% higher among females than among males, despite an only 30% higher fat percentage in females. A close association between degree of obesity and leptin concentrations was observed in both sexes. The correlation coefficient between fat mass and leptin concentration ranged between r = 0.467- 0.817 (p< 0.001 - 0.01). A close correlation between degree of weight loss and decrease in leptin concentrations was observed in both sexes. A 10.1 kg (9.6%) decrease in body weight among females was associated with a 32% decrease in leptin concentrations. The corresponding value among males for an 8.0 kg (8.6%) decrease was 29%. Changes in leptin concentrations were best explained by changes in fat mass among both males and females. Body fat distribution was also of importance, especially among females. Gender associated differences in leptin concentrations appear to be largely influenced by gender differences in body fat distribution.     

Effects of estradiol and progesterone on body composition, protein synthesis, and lipoprotein lipase in rats

Prior studies suggest that estradiol and progesterone regulate body composition in growing female rats. Because these studies did not consider the confounding effect of changes in food intake, it remains unclear whether ovarian hormones regulate body composition independently of their effects on food intake. We utilized a pair-feeding paradigm to examine the effects of these hormones on body composition. In addition, skeletal muscle protein fractional synthesis rate and adipose tissue lipoprotein lipase activity were measured to examine pathways of substrate deposition into fat and fat-free tissue. Female Sprague-Dawley rats [pubertal: 7-8 wk old; 190 +/- 0.5 (SE) g] were separated into four groups: 1) sham-operated (S; n = 8), 2) ovariectomized plus placebo (OVX; n = 8), 3) ovariectomized plus estradiol (OVX+E; n = 8), and 4) ovariectomized plus progesterone (OVX+P; n = 8). All ovariectomized groups were pair-fed to the S group. Body composition was measured using total body electrical conductivity. The relative increase in fat-free mass was greater (P < 0.01) in the OVX group (31 +/- 2%) than in the S (17 +/- 2%), OVX+E (18 +/- 2%), and OVX+P (22 +/- 2%) groups. The fractional synthetic rates of gastrocnemius muscle protein paralleled changes in fat-free mass: OVX had a higher (P < 0.05) synthesis rate (21 +/- 3%/day) than S (12 +/- 2%/day), OVX+E (11 +/- 2%/day), and OVX+P (8 +/- 1%/day) groups. Body fat increased in the S group (31 +/- 7%; P < 0.01), whereas the OVX groups lost fat (OVX: -10 +/- 7%; OVX+E: -15 +/- 7%; OVX+P: -13 +/- 7%). No differences in lipoprotein lipase were found. Our results suggest that estradiol and progesterone may regulate the growth of fat and fat-free tissues in female rats. Moreover, ovarian hormones may influence skeletal muscle growth through their effects on skeletal muscle protein synthesis.     

Relationship between Left Ventricle and Body Composition in Young Male and Female Athletes

Competitive sports induce gradual cardiac adaptations in young athletes. During growth, changes occur in their body composition. The purpose of this study is to provide the left ventricular parameters indexed for body composition during young athletes’ growth 220 young athletes (110 females and 110 males) aged from 8 to 19 years old were enrolled. An accurate body composition analysis and echocardiography were performed. The left ventricular parameters were then indexed to the body surface area formula with the data related to body composition (fat-free mass and body cellular mass). The left ventricular and body composition parameters increased continuously during growth and no differences between the sexes were found before puberty. Higher fat mass was found in females from 12 years old (Fat Mass Index: Female = 4.8 ± 1.8 kg/m², Male = 3.6 ± 0.9 kg/m²; p< 0.05). Cardiac differences started at 13 years old, with a greater left ventricular mass in males (Female = 110.9 ± 20.2 g, Male = 128.7 ± 23.7 g; p< 0.05). The indexing of the left ventricle to the body composition parameters increased the age of onset of these cardiological differences to 14 years old with fat-free mass (Female = 91.8 ± 18.7 g/m², Male = 105.0 ± 19.5 g/m²; p< 0.05), or to 15 years old with body cell mass (Female = 124.3 ± 17.9 g/m², Male = 145.8 ± 28.5 g/m²; p< 0.05). Differences between the sexes appear to start after puberty. The above indexing was used in order to normalize the differences between the sexes according to body composition. This study reports the reference values for age and gender of the left ventricular parameters indexed for metabolically active mass.     

限制能量平衡膳食联合运动干预对肥胖儿童身体成分、脂质代谢及肠道菌群的影响

摘要 目的：观察限制能量平衡膳食联合运动干预对肥胖儿童身体成分、脂质代谢及肠道菌群的影响。方法：选取2020年4月至2022年10月期间浙江大学医学院附属儿童医院收治的肥胖儿童104例作为研究对象。按照随机数字表法将肥胖儿童分为对照组（n=52,限制能量平衡膳食）和观察组（n=52,限制能量平衡膳食联合运动干预）。对比两组身体成分、脂质代谢及肠道菌群变化情况。结果：观察组干预2个月后体重、体质量指数（BMI）、去脂体重、脂肪量、体脂率低于对照组（P<0.05）。观察组干预2个月后总胆固醇（TC）、甘油三酯（TG）、低密度脂蛋白胆固醇（LDL-C）低于对照组;高密度脂蛋白胆固醇（HDL-C）高于对照组（P<0.05）。观察组干预2个月后肠球菌、大肠杆菌低于对照组;乳杆菌、双歧杆菌高于对照组（P<0.05）。结论：限制能量平衡膳食联合运动干预可有效改善肥胖儿童身体成分,调节脂质代谢及肠道菌群平衡。     

Relationship of fat mass and serum estradiol with lower extremity bone in persons with chronic spinal cord injury

In the spinal cord injury (SCI) population, a relationship between adiposity and leg bone has not been reported, nor one between serum estradiol and leg bone mass. A cross-sectional, comparative study of 10 male pairs of monozygotic twins discordant for SCI was performed. Relationships were determined among bone mineral density (BMD), bone mineral content (BMC), lean mass, fat mass, and serum sex steroids. In the twins with SCI, significant relationships were evident between leg BMD or BMC with total body percent fat (r2= 0.49, P < 0.05; r2= 0.45, P = 0.05), leg fat mass (r2 = 0.76, P < 0.0005; r2= 0.69, P = 0.005), and serum estradiol (r2= 0.40, P = 0.05; r2= 0.37, P = 0.05). By stepwise regression analysis, in the twins with SCI, leg fat mass was found to be the single most significant predictor of leg BMD or BMC (F = 12.01, r2= 0.76, P = 0.008; F = 50.87, r2= 0.86, P < 0.0001). In the able-bodied twins, leg lean mass correlated with leg BMD and BMC (r2= 0.58, P = 0.01; r2= 0.87, P = 0.0001). By use of within-pair differences, significant correlations were found for leg lean mass loss with leg BMD loss (r2= 0.56, P = 0.01) or leg BMC loss (r2= 0.64, P = 0.0005). In conclusion, in twins with SCI, significant correlations were observed between fat mass and leg BMD or BMC as well as between serum estradiol values and leg BMD. The magnitude of the leg muscle mass loss was correlated with the magnitude of bone loss.     

One- and two-year change in body composition as measured by DXA in a population-based cohort of older men and women.

Changing body composition has been suggested as a pathway to explain age-related functional decline. No data are available on the expected changes in body composition as measured by dual-energy X-ray absorptiometry (DXA) in a population-based cohort of older persons. Body composition data at baseline, 1-yr follow-up, and 2-yr follow-up was measured by DXA in 2,040 well-functioning black and white men and women aged 70-79 yr, participants of the Health, Aging, and Body Composition Study. After 2 yr, a small decline in total body mass was observed (men: -0.3%, women: -0.4%). Among men, fat-free mass and appendicular lean soft tissue mass (ALST) decreased by -1.1 and -0.8%, respectively, which was masked by a simultaneous increase in total fat mass (+2.0%). Among women, a decline in fat-free mass was observed after 2 yr only (-0.6%) with no change in ALST and body fat mass. After 2 yr, the decline in ALST was greater in blacks than whites. Change in total body mass was associated with change in ALST (r = +0.58 to +0.70; P < 0.0001). Among participants who lost total body mass, men lost relatively more ALST than women, and blacks lost relatively more ALST than whites. In conclusion, the mean change in body composition after a 1- to 2-yr follow-up was 1-2% with a high interindividual variability. Loss of ALST was greater in men compared with women, and greater in blacks compared with whites, suggesting that men and blacks may be more prone to muscle loss.     

Longitudinal body composition data in exclusively breast-fed infants: a multicenter study

Reference %fat and total fat-free mass data is necessary for evaluating growth in infants. We aimed to develop longitudinal %fat and total fat-free mass data in infants from birth to 6 months of age. An observational, multicenter, prospective cohort study was conducted with assessments at birth, 1 week, 2 weeks, 1, 2, 3, 4, 5, and 6 months of age. Subjects were exclusively breast-fed and were enrolled at three centers. Whole-body composition (i.e., % fat and total fat-free mass) were assessed using air-displacement plethysmography (ADP) (PEA POD; Life Measurement, Concord, CA). Maternal prepregnancy BMI, gestational weight gain, and infant anthropometric data were collected. A total of 160 infants (boys = 84) were assessed from birth to 4 months of age. Mean birth weight was 3.46 ± 0.39 kg % fat and fat-free mass significantly increased from birth to 4 months of age (P < 0.0001). Gender-specific %fat and total fat-free mass curves for infants from birth to 4 months of age were created. This study will be beneficial to health-care professionals in evaluating normal growth and nutritional patterns in the first months of life.     

Genetic selection, sex and feeding treatment affect the whole-body chemical composition of sheep

Hypotheses on total body chemical composition were tested using data from 350 Suffolk sheep grown to a wide range of live weights, and fed in a non-limiting way, or with reduced amounts of feed, or ad libitum on feeds of reduced protein content. The sheep were from an experiment where selection used an index designed to increase the lean deposition rate while restricting the fat deposition rate. Ultrasound muscle and fat depths were the only composition measurements in the index. The animals were males and females from a selection (S) line and its unselected control (C). The protein content of the lipid-free dry matter was unaffected by live weight, sex or feeding treatment with only a very small effect of genetic line (0.762 kg/kg in S and 0.753 kg/kg in C; P < 0.05). The form of the relationship between water and protein was not affected by any of the factors; in the different kinds of sheep it was consistent with no effect other than through differences in mature protein weight. The water : protein ratio at maturity was estimated as 3.45. Over the whole dataset, lipid weight (L) increased with protein weight (P) according to L = 0.3135 × P1.850. Allowing for this scaling, fatness increased on low-protein feeds, was greater in females than in males and in C than in S (P < 0.001). Lipid content (g/kg fleece-free empty body weight) was reduced by restricted feeding only in males at the highest slaughter weight (114 kg). The lines differed in lipid content (P < 0.001) with means of 265.1 g/kg for C and 237.3 g/kg for S. Importantly, there was no interaction between line and feeding treatments. A higher proportion of total body protein was in the carcass in S than in C (0.627 v. 0.610; P < 0.001). For lipid, the difference was reversed (0.736 v. 0.744; P < 0.05). The total energy content increased quadratically with slaughter weight. At a particular weight, the energy content of gain was higher in females than in males and in C than in S. Genetic selection affected body composition at a weight favouring the distribution of protein to the carcass and lipid to the non-carcass. Once allowing for effects of genetic selection, sex and feeding treatment on fatness, simple rules can be used to generate the chemical composition of sheep.     

Exercise without weight loss is an effective strategy for obesity reduction in obese individuals with and without Type 2 diabetes.

It is unclear whether chronic exercise without caloric restriction or weight loss is a useful strategy for obesity reduction in obese men with and without Type 2 diabetes (T2D). We examined the effects of exercise without weight loss on total and regional adiposity and skeletal muscle mass and composition in lean men and in obese men with and without T2D. Twenty-four men participated in 13 wk of supervised aerobic exercise, five times per week for 60 min at a moderate intensity (approximately 60% peak oxygen uptake). Total and regional body composition was measured by magnetic resonance imaging. Skeletal muscle composition was determined using computed tomography. Cardiorespiratory fitness was assessed using a graded maximal treadmill test. Body weight did not change within any group in response to exercise (P > 0.1). Significant reductions in total, abdominal subcutaneous, and visceral fat were observed within each group (P < 0.01). The reduction in total and abdominal subcutaneous fat was not different (P > 0.1) between groups; however, the reduction in visceral fat was greater (P < 0.01) in the obese and T2D groups by comparison to the lean group. A significant (P < 0.01) increase in total skeletal muscle, high-density muscle area, and mean muscle attenuation was observed independent of group, and these changes were not different between groups (P > 0.1). Accordingly, whole body fat-to-muscle ratio was increased (P < 0.01) independent of groups. In conclusion, regular exercise without weight loss is associated with a substantial reduction in total and visceral fat and in skeletal muscle lipid in both obesity and T2D.     

Determinants of insulin-stimulated glucose disposal in middle-aged, premenopausal women

Controversy exists regarding the relative importance of adiposity, physical fitness, and physical activity in the regulation of insulin-stimulated glucose disposal. To address this issue, we measured insulin-stimulated glucose disposal [mg. kg fat-free mass (FFM)(-1). min(-1); oxidative and nonoxidative components] in 45 nondiabetic, nonobese, premenopausal women (mean +/- SD; 47 +/- 3 yr) by use of hyperinsulinemic euglycemic clamp (40 mU. m(-2). min(-1)) and [6,6-2H2]glucose dilution techniques. We also measured body composition, abdominal fat distribution, thigh muscle fat content, maximal oxygen consumption (VO2 max), and physical activity energy expenditure ((2)H(2)(18)O kinetics) as possible correlates of glucose disposal. VO2 max was the strongest correlate of glucose disposal (r = 0.63, P < 0.01), whereas whole body and abdominal adiposity showed modest associations (range of r values from -0.32 to -0.46, P < 0.05 to P < 0.01). A similar pattern of correlations was observed for nonoxidative glucose disposal. None of the variables measured correlated with oxidative glucose disposal. The relationship of VO2 max to glucose disposal persisted after statistical control for FFM, percent body fat, and intra-abdominal fat (r = 0.40, P < 0.01). In contrast, correlations of total and regional adiposity measures to insulin sensitivity were no longer significant after statistical adjustment for VO2 max. VO2 max was the only variable to enter stepwise regression models as a significant predictor of total and nonoxidative glucose disposal. Our results highlight the importance of VO2 max as a determinant of glucose disposal and suggest that it may be a stronger determinant of variation in glucose disposal than total and regional adiposity in nonobese, nondiabetic, premenopausal women.