Changes in body composition with weight loss: obese subjects randomized to surgical and medical programs

Objective: To assess changes in body composition with weight loss in obese subjects randomized to a laparoscopic adjustable gastric band surgical program or a medical program using a very‐low‐energy diet and orlistat. Research Methods and Procedures: Using body composition measurements by DXA, neutron activation for total body nitrogen, and whole body γ counting for total body potassium, we studied changes in fat mass, fat distribution, fat‐free mass, total bone mineral content, total body protein, and body cell mass at 6 (n = 61 paired) and 24 months (n = 53 paired) after randomization. Results: At 24 months, the surgical group had lost significantly more weight (surgical, 20.3 ± 6.5 kg; medical, 5.9 ± 8.0 kg). There was favorable fat‐free mass to fat mass loss ratios for both groups (surgical, 1:5.5; medical, 1:5.9). Changes in total body nitrogen or potassium were favorable in each group. A small reduction in mean bone mineral content occurred throughout the study but was not associated with extent of weight loss or treatment group. At 6 months, weight loss for both groups was similar (surgical, 14.1 ± 4.5 kg; medical, 13.3 ± 7.3 kg). The medical program subjects lost less fat‐free mass and skeletal muscle and had increased total body protein. The proportion of body fat to limb fat remained remarkably constant throughout the study. Discussion: Weight loss programs used in this study induced fat loss without significant deleterious effects on the components of fat‐free mass.     

BODY FAT, PUBERTY AND FERTILITY

1. The high percentage of fat, about 26–28% in the mature human female, may influence reproductive ability directly through two mechanisms: ( a ) fat converts androgens to oestrogens; ( b ) relative fatness influences the direction of metabolism of oestrogen to the most potent or least potent forms. The relative degree of fatness thus is directly related to both the quantity of circulating oestrogen and the biological effectiveness of the oestrogen. This is a neat mechanism for relating rates of growth, nutrition and energy outputs to the energy requirements for reproduction. Fat is the most labile body tissue; it therefore reflects environmental changes more rapidly than other tissues of the body.
2. The slow maturation of the hypothalamus and pituitary up to menarche, or first oestrus, is accompanied by a slow maturation of the body, which changes not only in size but in the relative proportion of bone, muscle, and fat. Evidence is presented that a particular threshold ratio of fat to lean mass is normally necessary for puberty and the maintenance of female reproductive ability in the human and in the rat. The synchronizing mechanisms may be metabolic, relating food intake to core temperature and/or fat storage.
3. Undernutrition and weight loss in the range of 10–15 % of normal weight for height delays menarche and causes amenorrhoea. Ballet dancers and athletes also have delayed menarche and amenorrhoea. The cessation of reproduction in both groups can be considered adaptive. Refeeding and/or cessation of intense activity results in the initiation or resumption of menstrual cycles after varying periods of time. A necessary threshold weight for height can be predicted from a fatness index.
4. Differences in the natural fertility of historical and contemporary populations may be explained by a direct effect of food intake and energy outputs on fecundity.
5. The late maturing fat - 'sex fat' - may have a special role in reproduction.     

The role of leptin and orexins in the dysfunction of hypothalamo-pituitary-gonadal regulation and in the mechanism of hyperactivity in patients with anorexia nervosa

Anorexia nervosa (AN) belongs to a group of eating disorders and is characterized by extreme body weight loss. AN patients show combination of physical, psychological and behavioral disturbances. Neuropeptides partly control energy homeostasis and modulate hormone release. Leptin, a peptide secreted by adipocytes, may influence the interactions between central and peripheral signals. Hypoleptinaemia found in AN is connected with disturbed control of appetite and hormonal dysfunction as well as has implications for the hypothalamo-pituitary-gonadal axis, bone mineral density and physical hyperactivity. Low leptin levels are increased with refeeding. However, the prolonged hypoleptinaemia in weight recovered AN patients may result in persistent hypothalamic amenorrhoea. The hyperactivity has been observed in 31-80 % of AN cases. The mechanisms underlying the hyperactivity found in patients with anorexia nervosa seem to be more complicated as many factors including neuropeptides may be involved. Orexins may affect not only appetite but also behavior and psychophysical activity as they may regulate reproductive and stress hormone secretion, stimulate a variety of stereotypic behaviors including eating and stress reaction, and affect the hypothalamo-pituitary-adrenal (HPA) axis, alter glucocorticoid and catecholamine secretion and activate the sympathetic nervous system. Orexins influence the mechanism regulating arousal and sleep, cardiovascular function, temperature, metabolic rate and locomotive activity. It is worth considering how abnormal activity of hypothalamic neuropeptides or their receptors may play a role in the mechanisms of hyperactivity, disturbed control of appetite and hormonal dysfunction in patients with anorexia nervosa.     

Anorexia nervosa viewed as an extreme weight condition: genetic implications

In anorexia nervosa, psychopathological features and reduced body weight are inseparable, suggesting a prominent role of behavioral factors in achievement and maintenance of extreme underweight. Due to the considerably higher prevalence of this eating disorder in females, anorexia nervosa contributes to the left end of the distribution of the body mass index, especially in the female sex. By reviewing the relevant literature we examined whether genetic research in anorexia nervosa can profit from considering this disorder as an extreme weight condition. For this purpose we compared genetic studies pertaining to both anorexia nervosa and the heritability of the body mass index. Whereas previous genetic studies in anorexia nervosa have mostly concentrated on the assessment of the familial psychopathology, further studies are warranted that additionally attempt to analyze the complex phenotype body weight in relatives of affected probands. Further insight into pathogenetic mechanisms underlying anorexia nervosa might be gained by contrasting the epidemiological, psychopathological and prognostic factors with those in severe obesity. Thus, epidemiological studies suggest that females are more likely to develop both extreme underweight and extreme obesity. A possible explanation for this phenomenon is that the, on average, higher percentage of total body weight composed of fat mass might predispose females towards the development of both extreme weight conditions.     

Changes in the chemical composition of fat body during the last larval instar of Manduca sexta.

The fat body increases in weight throughout the last larval instar in spite of the loss in total body weight during the wandering and prepupal stages. The protein content of fat body increases dramatically and is greatly responsible for the increase in fat body weight in the wandering and prepupal stages. Lipids do not contribute significantly to the fat body weight gain except during the feeding stage. The amount of total fat body RNA increases until wandering then drops abruptly in the prepupal stage. The total amount of fat body DNA peaks before the onset of wandering and prepupal stages.     

Preferential loss of body fat during starvation in dietary obese rats.

This study was undertaken to examine whether diet-induced obesity alters the amount and/or composition of weight lost during starvation. The amount and composition of weight lost during a 4-day period of starvation was determined before and at 17, 30 and 42 weeks after rats (350 g of body weight) were given a high fat diet (HFD). To control for effects of aging, a second group of rats, fed standard laboratory chow, was also subjected to similar periods of starvation. Although total weight loss during starvation was never greater for HFD rats than for chow-fed rats, the former group showed a clear patter of increasing loss of body fat and total energy and conservation of fat-free tissues with periods of starvation later in life. In addition, chow-fed rats showed substantial energy conservation during each period of starvation (i.e. they lost less energy each day than their pre-starvation energy requirements). In contrast, HFD rats demonstrated substantial energy conservation only at 17 weeks and not at 30 or 42 weeks; during the last period of starvation, their average daily loss of carcass energy exceeded their pre-starvation energy requirements. This suggests the increased fat mass of these rats may have led to increased fuel availability and to an increased metabolic rate during starvation. If these results are applicable to humans, the more obese subjects are likely to show greater total loss of energy than lean subjects, but show a lesser loss of lean body mass, at least initially. If protein requirements are reflected by the ability to mobilize protein during food restriction, protein requirements would be substantially lower in the dietary obese rats than in controls. In summary, diet-induced obesity leads to preferential loss of body fat and conservation of lean mass during starvation.     

Lean, fat and bone masses are influenced by orchidectomy in the rat. A densitometric X-ray absorptiometric study

In man, hypogonadism is a risk factor for osteoporosis. Orchidectomy (ORX) in the rat leads to an imbalance between resorption and formation resulting in bone loss. We have measured whole body weight, lean and fat mass, whole bone mass (BMC) in the ORX rat model by dual X-ray densitometry (DXA). Forty-eight male Wistar rats (18-19 weeks old) were studied at 2, 4, 8 and 16 weeks. In each group, 6 rats were ORX and 6 sham-operated were used as control. DXA was performed on the whole body and isolated tibia. The whole body weight of the ORX animals became significantly decreased only at 16 weeks. Whole body BMC was reduced from 8 weeks in the ORX group. The most striking result was a net decrease in lean mass that reached -15.7% at 16 weeks. On the other hand, fat mass remained unchanged during the time series in the ORX animals.     

Body Composition Changes in Caucasian and African American Children and Adolescents with Obesity Using Dual-Energy X-ray Absorptiometry Measurements after a 10-Week Weight Loss Program

Objective : Changes in body composition during a weight loss program have not been described in children. We wanted to test the hypothesis that weight loss can be achieved while maintaining total body fat-free mass. Research Methods and Procedures : We determined body composition changes by using dual-energy X-ray absorptiometry measured at baseline and after the first 10 weeks of a multidisciphnary weight loss program. The program consisted of 10 weekly group sessions where the children were provided instruction in lifestyle modification, including diet and exercise. Program leaders included a pediatrician, psychologist, registered dietitian, and exercise instructor. Results : We studied 59 obese children, mean (± SD) age 12.8 ± 2.6 years, 29% boys and 71% girls, 49% Caucasian, and 51% African American. At enrollment, the children's mean height and body mass index were 157 cm and 38.9 kg/m², respectively. The children's dual-energy X-ray absorptiometry-derived mean at baseline and at 10 weeks and corresponding p values were: weight (94.6 kg vs. 92.3 kg, p<0.0001), total body fat mass (46.9 kg vs. 44.3 kg, p<0.0001), percentage total body fat (49.2% vs. 47.5%, p<0.0001), total trunk mass (43.0 kg vs. 41.5 kg,p<0.0001), total trunk fat (21.2 kg vs. 20.0 kg, p<0.0001), total body fat-free mass (47.6 kg vs. 47.9 kg, p = 0.33), total body bone mass (2.7 kg vs. 2.7 kg, p = 0.99), and total body bone mineral density (1.14 g/cm² vs. 1.15 g/cm², p = 0.0119). The children's race, gender, or Tanner stage did not affect these changes. Discussion : Decreases in total body fat mass was achieved, and total body fat-free mass was maintained among boy and girl Caucasian and African American children participating in this lifestyle modification weight loss program.     

Fatness, menarche, and female fertility

It is hypothesized that a particular ratio of fat to lean mass is required for menarche and the maintenance of regular menstrual cycles. Females who lose 10-15% of normal weight for height, equivalent to a loss of 1/3 of body fat, become amenorrheic, presumably due to hypothalamic dysfunction. Adipose tissue may provide signals to the central nervous system and gonadotropin regulatory areas either directly, by estrogen production, or indirectly, by the effects of relative fatness on temperature control and metabolic rate, or by both means. Women with hypothalamic dysfunction experience changes in the secretion of gonadotropins, luteinizing hormone, follicle-stimulating hormone, and estrogen. Weight gain restores postmenarcheal secretion patterns. This approach suggests that the secular trend toward earlier age at menarche reflects earlier attainment of critical weight as a result of improved nutrition and child care. In many societies, subnutrition may explain the observed submaximum fertility. This suggests a need to integrate family planning programs with nutrition programs in many developing countries. It is important to note that the prediction of the minimum weight for height for onset and maintenance of ovulatory cycles is from total water as percentage of body weight. Although the percentage of fat in the body is inversely related to the percent of body water, only the latter is predictive. Successful prediction of the minimum weights for height is related to a lean mass/fat ratio represented by about 17% fat of body weight at menarche and 22% of body weight at the completion of growth at age 18 years.     

Relation between Aspects of Nutritional Disturbance and Menstrual Activity in Primary Anorexia Nervosa

A significantly high number of patients with anorexia nervosa are overweight immediately before the onset of the condition. This premorbid weight may be a feature of their constitution but is sometimes a more transitory phenomenon. Menstruation ceases early in the condition but usually within the context of significant weight loss. However, the subsequent amenorrhoea, related to factors that presumably may not begin to operate until several weeks later, may be a symptom which first draws attention to the condition.Treatment included the restitution of body weight to the matched population mean weight for each patient. This may be important, as the mean weight at which menstrual activity returned was not significantly different from the matched population mean weight. A further treatment aim, so far as nutrition was concerned. was restoration of regular and reasonable feeding behaviour, including adequate carbohydrate ingestion. It is suggested that these findings support the view that the nutritional disturbance in anorexia nervosa is an important factor affecting menstrual activity.     

Preadipocyte factor-1 concentrations in patients with anorexia nervosa: the influence of partial realimentation

Preadipocyte factor-1 (Pref-1) is a member of epidermal growth-factor like family of proteins that regulates adipocyte and osteoblast differentiation. Experimental studies suggest that circulating Pref-1 levels may be also involved in the regulation of lipid and glucose metabolism and energy homeostasis. We hypothesized that alterations in Pref-1 levels may contribute to the ethiopathogenesis of anorexia nervosa or its underlying metabolic abnormalities. We measured Pref-1 concentrations and other hormonal, biochemical and anthropometric parameters in eighteen patients with anorexia nervosa and sixteen healthy women and studied the influence of partial realimentation of anorexia nervosa patients on these parameters. The mean duration of realimentation period was 46±2 days. At baseline, anorexia nervosa patients had significantly decreased body mass index, body weight, body fat content, fasting glucose, serum insulin, TSH, free T4, leptin and total protein. Partial realimentation improved these parameters. Baseline serum Pref-1 levels did not significantly differ between anorexia nervosa and control group (0.26±0.02 vs. 0.32±0.05 ng/ml, p=0.295) but partial realimentation significantly increased circulating Pref-1 levels (0.35±0.04 vs. 0.26±0.02 ng/ml, p<0.05). Post-realimentation Pref-1 levels significantly positively correlated with the change of body mass index after realimentation (r=0.49, p<0.05). We conclude that alterations in Pref-1 are not involved in the ethiopathogenesis of anorexia nervosa but its changes after partial realimentation could be involved in the regulation of adipose tissue expansion after realimentation.     

Body composition characteristics, sex hormone levels and circadian gonadotropin fluctuations in infertile young women

The present study dealt with the interaction between body composition estimated by means of dual energy x-ray absorptiometry, sex-specific fat distribution and sex hormone levels (LH, FSH, estradiol, prolactin, DHEA-S, androstendione, testosterone and SHBG) as well as LH and FSH fluctuations in infertile young women ageing between 18 and 30 years (x = 23.4 yr). Twenty patients suffered from polycystic ovaries (PCO), 15 women suffering from a mild anorexia nervosa were amenorrhoeic for more than one year. Marked associations between estradiol, testosterone, SHBG as well as the FSH output and body fat, bone mass and fat distribution were documented. PCO patients exhibited a high weight status and a typical android fat distribution which signals infertility comparable to postmenopausal women. In contrast, although anorexia patients had pathological decreased estrogen levels and were infertile at the time of investigation, their fat distribution was be classified as 'ypergynoid' and signals potential reproductive capability after a sufficient weight gain.     

Resting Energy Expenditure Changes With Weight Loss: Racial Differences

It is controversial whether weight loss reduces resting energy expenditure (REE) to a different magnitude in black and white women. This aim of this study was to determine whether changes in REE with weight loss were different between black and white postmenopausal women, and whether changes in body composition (including regional lean and fat mass) were associated with REE changes within each race. Black (n = 26) and white (n = 65) women (age = 58.2 ± 5.4 years, 25 < BMI < 40 kg/m²) completed a 20‐week weight‐loss intervention. Body weight, lean and fat mass (total body, limb, and trunk) via dual‐energy X‐ray absorptiometry, and REE via indirect calorimetry were measured before and after the intervention. We found that baseline REE positively correlated with body weight, lean and fat mass (total, limb, and trunk) in white women only (P < 0.05 for all). The intervention decreased absolute REE in both races similarly (1,279 ± 162 to 1,204 ± 169 kcal/day in blacks; 1,315 ± 200 to 1,209 ± 185 kcal/day in whites). REE remained decreased after adjusting for changes in total or limb lean mass in black (1,302–1,182 kcal/day, P = 0.043; 1,298–1,144 kcal/day, P = 0.006, respectively), but not in white, women. Changes in REE correlated with changes in body weight (partial r = 0.277) and fat mass (partial r = 0.295, 0.275, and 0.254 for total, limb, and trunk, respectively; P < 0.05) independent of baseline REE in white women. Therefore, with weight loss, REE decreased in proportion to the amount of fat and lean mass lost in white, but not black, women.     

Markers of inflammation and fat distribution following weight loss in African-American and white women

Changes in markers of inflammation (MOI) and fat distribution with weight loss between African-American (AA) and white (W) women have yet to be characterized. The purpose of this study was to examine potential ethnic differences in MOI and regional fat distribution with weight loss, and identify the associations between these markers and changes in regional fat distribution with weight loss among AA and W women. Subjects were 126 healthy, premenopausal women, BMI 27-30 kg/m(2). They were placed on a weight-loss intervention consisting of diet and/or exercise until a BMI <25 was achieved. Fat distribution was measured with computed tomography, and body composition with dual-energy X-ray absorptiometry. Serum concentrations of tumor necrosis factor-α (TNF-α), soluble TNF receptor-I (sTNFR-I), sTNFR-II, C-reactive protein (CRP), and interleukin-6 (IL-6) were assessed. All MOI and adiposity measures significantly decreased with weight loss. Significant ethnic differences with weight loss were observed for fat mass, body fat, intra-abdominal adipose tissue (IAAT), sTNFR-I, and sTNFR-II. Mixed-model analysis indicated that adjusting for change in IAAT explained ethnic differences in change in TNF-α and the decrease in TNF-α with weight loss, while total fat mass only explained the decrease in sTNFR-I and sTNFR-II with weight loss. In conclusion, all MOI decreased following weight loss among W, whereas only IL-6 and CRP decreased following weight loss in AA. The most distinct phenotypic difference observed was a greater impact of weight loss on TNF-α in W compared to AA, which was directly associated with IAAT in W.     

Effects of conjugated linoleic acid supplementation during resistance training on body composition,bone density,strength, and selected hematological markers

Conjugated linoleic acids (CLA) are essential fatty acids that have been reported in animal studies to decrease catabolism, promote fat loss, increase bone density, enhance immunity, and serve as an antiatherogenic and anticarcinogenic agent. For this reason, CLA has been marketed as a supplement to promote weight loss and general health. CLA has also been heavily marketed to resistance-trained athletes as a supplement that may help lessen catabolism, decrease body fat, and promote greater gains in strength and muscle mass during training. Although basic research is promising, few studies have examined whether CLA supplementation during training enhances training adaptations and/or affects markers of health. This study evaluated whether CLA supplementation during resistance training affects body composition, strength, and/or general markers of catabolism and immunity. In a double-blind and randomized manner, 23 experienced, resistance-trained subjects were matched according to body mass and training volume and randomly assigned to supplement their diet with 9 g;pdd(-1) of an olive oil placebo or 6 g;pdd(-1) of CLA with 3 g;pdd(-1) of fatty acids for 28 days. Prior to and following supplementation, fasting blood samples, total body mass, and dual-energy X-ray absorptiometry (DEXA) determined body composition, and isotonic bench press and leg press 1 repetition maximums (1RMs) were determined. Results revealed that although some statistical trends were observed with moderate to large effect sizes, CLA supplementation did not significantly affect (p > 0.05) changes in total body mass, fat-free mass, fat mass, percent body fat, bone mass, strength, serum substrates, or general markers of catabolism and immunity during training. These findings indicate that CLA does not appear to possess significant ergogenic value for experienced resistance-trained athletes.     

Long-Term Physiological Alterations and Recovery in a Mouse Model of Separation Associated with Time-Restricted Feeding: A Tool to Study Anorexia Nervosa Related Consequences

Background

Anorexia nervosa is a primary psychiatric disorder, with non-negligible rates of mortality and morbidity. Some of the related alterations could participate in a vicious cycle limiting the recovery. Animal models mimicking various physiological alterations related to anorexia nervosa are necessary to provide better strategies of treatment.

Aim

To explore physiological alterations and recovery in a long-term mouse model mimicking numerous consequences of severe anorexia nervosa.

Methods

C57Bl/6 female mice were submitted to a separation-based anorexia protocol combining separation and time-restricted feeding for 10 weeks. Thereafter, mice were housed in standard conditions for 10 weeks. Body weight, food intake, body composition, plasma levels of leptin, adiponectin, IGF-1, blood levels of GH, reproductive function and glucose tolerance were followed. Gene expression of several markers of lipid and energy metabolism was assayed in adipose tissues.

Results

Mimicking what is observed in anorexia nervosa patients, and despite a food intake close to that of control mice, separation-based anorexia mice displayed marked alterations in body weight, fat mass, lean mass, bone mass acquisition, reproductive function, GH/IGF-1 axis, and leptinemia. mRNA levels of markers of lipogenesis, lipolysis, and the brown-like adipocyte lineage in subcutaneous adipose tissue were also changed. All these alterations were corrected during the recovery phase, except for the hypoleptinemia that persisted despite the full recovery of fat mass.

Conclusion

This study strongly supports the separation-based anorexia protocol as a valuable model of long-term negative energy balance state that closely mimics various symptoms observed in anorexia nervosa, including metabolic adaptations. Interestingly, during a recovery phase, mice showed a high capacity to normalize these parameters with the exception of plasma leptin levels. It will be interesting therefore to explore further the central and peripheral effects of the uncorrected hypoleptinemia during recovery from separation-based anorexia.     

生物电阻抗法测定广西京族的体成分

本文利用生物电阻抗法对广西京族的体成分进行了测定,初步分析了其体成分形成的原因。研究组于2020年12月在广西壮族自治区东兴市“京族三岛”测定了430例京族成人（男182例,女248例）的16项指标。结果表明,京族男、女性的体质量、总肌肉量、躯干肌肉量、推定骨量、总能量代谢与年龄呈显著负相关。体成分随年龄增长而发生的变化,主要是自然的生理变化和劳动强度下降所致。随着年龄增长,男性的体脂率升高,这主要是躯干脂肪增多造成的。京族男性的体质量、总肌肉量、推定骨量、总能量代谢、水分率、四肢和躯干肌肉量均大于女性,而体脂率、四肢和躯干脂肪率均小于女性。京族男性比女性拥有更大的体质量和更高比例的骨骼肌,这两方面因素再加上劳动强度的差异,可能导致男性肌肉量、骨量、脂肪率等体成分与女性存在差异。总体来看,京族成人身体偏胖,脂肪含量较高,身体含水量基本正常,体成分特征与同为南亚语系或同在沿海地区的其他中国族群并不相似,而相对更接近于中国蒙古族,并且表现在体质量、体脂率、水分率等方面接近。生活环境、社会经济、日常饮食和劳动强度等因素是导致京族成人体质量及体脂率较高的原因。     

Ghrelin and the Hyposomatotropism of Obesity

Objective: Human obesity is characterized by growth hormone (GH) deficiency, which appears primarily related to a central pattern of obesity and is reverted on weight loss. As yet, the metabolic basis of the GH deficiency remains to be elucidated. The recently discovered endogenous ligand for the GH secretagogue receptor, ghrelin, stimulates GH secretion when administered to rodents or healthy humans. It may thus be hypothesized that low ghrelin levels underlie the hyposomatropism in obesity. Research Methods and Procedures: We have tested this hypothesis in individuals with widely varying body mass and fat distribution and evaluated whether the improved GH concentrations on weight loss are associated with enhanced ghrelin levels. Results: Both plasma GH and ghrelin levels were reciprocally related with body mass index (r = −0.67, p < 0.001). However, whereas 24-hour GH secretion was negatively related to the visceral fat area (r = −0.72, p < 0.01), ghrelin levels showed a positive relationship with the visceral fat area (r = 0.49, p < 0.02). Weight loss resulted in increased GH secretion (median 24-hour GH area under the curve: 1983 vs. 4024 mU/day before and after weight loss, respectively; p < 0.01) but did not affect ghrelin levels. No relationship could be found between GH and ghrelin plasma levels in obese subjects when comparing diurnal concentration profiles. Discussion: We showed that plasma ghrelin and GH levels are both reciprocally related with body mass index, but no causative relationship could be demonstrated between low ghrelin levels and the hyposomatropism in human obesity.     

Weight stability masks sarcopenia in elderly men and women

Skeletal muscle loss or sarcopenia in aging has been suggested in cross-sectional studies but has not been shown in elderly subjects using appropriate measurement techniques combined with a longitudinal study design. Longitudinal skeletal muscle mass changes after age 60 yr were investigated in independently living, healthy men (n = 24) and women (n = 54; mean age 73 yr) with a mean +/- SD follow-up time of 4.7 +/- 2.3 yr. Measurements included regional skeletal muscle mass, four additional lean components (fat-free body mass, body cell mass, total body water, and bone mineral), and total body fat. Total appendicular skeletal muscle (TSM) mass decreased in men (-0.8 +/- 1.2 kg, P = 0.002), consisting of leg skeletal muscle (LSM) loss (-0.7 +/- 0.8 kg, P = 0.001) and a trend toward loss of arm skeletal muscle (ASM; -0.2 +/- 0.4 kg, P = 0.06). In women, TSM mass decreased (-0.4 +/- 1.2 kg, P = 0.006) and consisted of LSM loss (-0.3 +/- 0.8 kg, P = 0.005) and a tendency for a loss of ASM (-0.1 +/- 0.6 kg, P = 0.20). Multiple regression modeling indicates greater rates of LSM loss in men. Body weight in men at follow-up did not change significantly (-0.5 +/- 3.0 kg, P = 0.44) and fat mass increased (+1.2 +/- 2.4 kg, P = 0.03). Body weight and fat mass in women were nonsignificantly reduced (-0.8 +/- 3.9 kg, P = 0.15 and -0.8 +/- 3.5 kg, P = 0.12). These observations suggest that sarcopenia is a progressive process, particularly in elderly men, and occurs even in healthy independently living older adults who may not manifest weight loss.     

Comparison of DXA and CT in the Assessment of Body Composition in Premenopausal Women With Obesity and Anorexia Nervosa

Accurate methods for assessing body composition in subjects with obesity and anorexia nervosa (AN) are important for determination of metabolic and cardiovascular risk factors and to monitor therapeutic interventions. The purpose of our study was to assess the accuracy of dual‐energy X‐ray absorptiometry (DXA) for measuring abdominal and thigh fat, and thigh muscle mass in premenopausal women with obesity, AN, and normal weight compared to computed tomography (CT). In addition, we wanted to assess the impact of hydration on DXA‐derived measures of body composition by using bioelectrical impedance analysis (BIA). We studied a total of 91 premenopausal women (34 obese, 39 with AN, and 18 lean controls). Our results demonstrate strong correlations between DXA‐ and CT‐derived body composition measurements in AN, obese, and lean controls (r = 0.77–0.95, P < 0.0001). After controlling for total body water (TBW), the correlation coefficients were comparable. DXA trunk fat correlated with CT visceral fat (r = 0.51–0.70, P < 0.0001). DXA underestimated trunk and thigh fat and overestimated thigh muscle mass and this error increased with increasing weight. Our study showed that DXA is a useful method for assessing body composition in premenopausal women within the phenotypic spectrum ranging from obesity to AN. However, it is important to recognize that DXA may not accurately assess body composition in markedly obese women. The level of hydration does not significantly affect most DXA body composition measurements, with the exceptions of thigh fat.