Sarcopenic Obesity Predicts Instrumental Activities of Daily Living Disability in the Elderly

Objective: To determine the association of sarcopenic obesity with the onset of Instrumental Activities of Daily Living (IADL) disability in a cohort of 451 elderly men and women followed for up to 8 years. Research Methods and Procedures: Sarcopenic obesity was defined at study baseline as appendicular skeletal muscle mass divided by stature squared <7.26 kg/m² in men and 5.45 kg/m² in women and percentage body fat greater than the 60th percentile of the study sample (28% body fat in men and 40% in women). Incident disability was defined as a loss of two or more points from baseline score on the IADL. Subjects with disability at baseline (scores < 8) were excluded. Cox proportional hazards analysis was used to determine the association of baseline sarcopenic obesity with onset of IADL disability, controlling for potential confounders. Results: Subjects with sarcopenic obesity at baseline were two to three times more likely to report onset of IADL disability during follow‐up than lean sarcopenic or nonsarcopenic obese subjects and those with normal body composition. The relative risk for incident disability in sarcopenic obese subjects was 2.63 (95% confidence interval, 1.19 to 5.85), adjusting for age, sex, physical activity level, length of follow‐up, and prevalent morbidity. Discussion: This is the first study, to our knowledge, to indicate that sarcopenic obesity is independently associated with and precedes the onset of IADL disability in the community‐dwelling elderly. The etiology of sarcopenic obesity is unknown but may include a combination of decreases in anabolic signals and obesity‐associated increases in catabolic signals in old age.     

Comparison of Overall Obesity and Body Fat Distribution in Predicting Risk of Mortality

Results of studies comparing overall obesity and abdominal adiposity or body fat distribution with risk of mortality have varied considerably. We compared the relative importance and joint association of overall obesity and body fat distribution in predicting risk of mortality. Participants included 5,799 men and 6,429 women aged 30–102 years enrolled in the third National Health and Nutrition Examination Survey who completed a baseline health examination during 1988–1994. During a 12‐year follow‐up (102,172 person‐years), 1,188 men and 925 women died. In multivariable‐adjusted analyses, waist‐to‐thigh ratio (WTR) in both sexes (P_trend <0.01 for both) and waist‐to‐hip ratio (WHR) in women (P_trend 0.001) were positively associated with mortality in middle‐aged adults (30–64 years), while BMI and waist circumference (WC) exhibited U‐ or J‐shaped associations. Risk of mortality increased with a higher WHR and WTR among normal weight (BMI 18.5–24.9 kg/m²) and obese (BMI ≥30.0 kg/m²) adults. In older adults (65–102 years), a higher BMI in both sexes (P_trend <0.05) and WC in men (P_trend 0.001) were associated with increased survival, while remaining measures of body fat distribution exhibited either no association or an inverse relation with mortality. In conclusion, ratio measures of body fat distribution are strongly and positively associated with mortality and offer additional prognostic information beyond BMI and WC in middle‐aged adults. A higher BMI in both sexes and WC in men were associated with increased survival in older adults, while a higher WHR or WTR either decreased or did not influence risk of death.     

Early cartilage abnormalities at the hip are associated with obesity and body composition measures – a 3.0T MRI community-based study

IntroductionAlthough obesity is a risk factor for hip osteoarthritis (OA), the role of body composition, if any, is unclear. This study examines whether the body mass index (BMI) and body composition are associated with hip cartilage changes using magnetic resonance imaging (MRI) in community-based adults.Methods141 community-based participants with no clinical hip disease, including OA, had BMI and body composition (fat mass and fat free mass) measured at baseline (1990 to 1994), and BMI measured and 3.0 T MRI performed at follow-up (2009–2010). Femoral head cartilage volume was measured and femoral head cartilage defects were scored in the different hip regions.ResultsFor females, baseline BMI (β = −26 mm³, 95% Confidence interval (CI) -47 to −6 mm³, p = 0.01) and fat mass (β = −11 mm³, 95% CI −21 to −1 mm³, p = 0.03) were negatively associated with femoral head cartilage volume. Also, while increased baseline fat mass was associated with an increased risk of cartilage defects in the central superolateral region of the femoral head (Odds Ratio (OR) = 1.08, 95% CI 1.00–1.15, p = 0.04), increased baseline fat free mass was associated with a reduced risk of cartilage defects in this region (OR = 0.82, 95% CI 0.67–0.99; p = 0.04). For males, baseline fat free mass was associated with increased femoral head cartilage volume (β = 40 mm³, 95% CI 6 to 74 mm³, p = 0.02).ConclusionsIncreased fat mass was associated with adverse hip cartilage changes for females, while increased fat free mass was associated with beneficial cartilage changes for both genders. Further work is required to determine whether modifying body composition alters the development of hip OA.     

A comparison of adiposity measures as predictors of all-cause mortality: the Melbourne Collaborative Cohort Study

Objective: Our goal was to examine five different measures of adiposity as predictors of all‐cause mortality. Research Methods and Procedures: Subjects were 16,969 men and 24,344 women enrolled between 1990 and 1994 in the Melbourne Collaborative Cohort Study (27 to 75 years of age). There were 2822 deaths over a median follow‐up period of 11 years. BMI, waist circumference, and waist‐to‐hip ratio were obtained from direct anthropometric measurements. Fat mass and percentage fat were estimated by bioelectric impedance analysis. Results: Comparing the top quintile with the second quintile, for men there was an increased risk of between 20% and 30% for all‐cause mortality associated with each of the anthropometric measures. For women, there was an increased risk of 30% (95% confidence interval for hazard ratio, 1.1–1.6) observed for waist circumference and 50% (1.2–1.8) for waist‐to‐hip ratio, but little or no increased risk for BMI, fat mass, and percentage fat. Waist‐to‐hip ratio was positively and monotonically associated with all‐cause mortality for both men and women. There was a linear association between waist circumference and all‐cause mortality for men, whereas a U‐shaped association was observed for women. Discussion: Measures of central adiposity were better predictors of mortality in women in the Melbourne Collaborative Cohort Study compared with measures of overall adiposity. We recommend measuring waist and hip circumferences in population studies investigating the risk of all‐cause mortality associated with obesity. The use of additional measures such as bioelectric impedance is not justified for this outcome.     

A Prospective Study of Adiposity and All‐Cause Mortality: The Malmö Diet and Cancer Study

Objective: This study aims to examine the association between various measures of adiposity and all‐cause mortality in Swedish middle‐aged and older men and women and, additionally, to describe the influences of age and sex on these associations. Research Methods and Procedures: A prospective analysis was performed in a cohort of 10,902 men and 16,814 women ages 45 to 73 years who participated in the Malmö Diet and Cancer Study in Sweden. Baseline examinations took place between 1991 and 1996, and 982 deaths were documented during an average follow‐up of 5.7 years. All‐cause mortality was related to the following variables measured at baseline: body mass index (BMI), percentage of body fat, lean body mass (LBM), and waist‐to‐hip ratio (WHR), with adjustment for age and selected covariates. Body composition data were derived from bioelectrical impedance analysis. Results: The association between percentage of body fat and mortality was modified by age, particularly in women. For instance, fatness was associated with excess mortality in the younger women but with reduced mortality in the older women. Weaker associations were seen for BMI than for percentage of body fat in both sexes. Placement in the top quintiles of waist‐to‐hip ratio, independent of overall body fat, was a stronger predictor of mortality in women than in men. The observed associations could not be explained by bias from early death or antecedent disease. Discussion: The findings reveal sex and age differences for the effects of adiposity and WHR on mortality and indicate the importance of considering direct measures of adiposity, as opposed to BMI, when describing obesity‐related mortality risks.     

FTO Genotype Is Associated With Exercise Training–induced Changes in Body Composition

The fat mass (FM) and obesity‐associated (FTO) gene is the first obesity‐susceptibility gene identified by genome‐wide association scans and confirmed in several follow‐up studies. Homozygotes for the risk allele (A/A) have 1.67 times greater risk of obesity than those who do not have the allele. However, it is not known whether regular exercise‐induced changes in body composition are influenced by the FTO genotype. The purpose of our study was to test whether the FTO genotype is associated with exercise‐induced changes in adiposity. Body composition was derived from underwater weighing before and after a 20‐week endurance training program in 481 previously sedentary white subjects of the HERITAGE Family Study. FTO single‐nucleotide polymorphism (SNP) rs8050136 was genotyped using Illumina GoldenGate assay. In the sedentary state, the A/A homozygotes were significantly heavier and fatter than the heterozygotes and the C/C homozygotes in men (P = 0.004) but not in women (P = 0.331; gene‐by‐sex interaction P = 0.0053). The FTO genotype was associated with body fat responses to regular exercise (P < 0.005; adjusted for age, sex, and baseline value of response trait): carriers of the C allele showed three times greater FM and %body fat losses than the A/A homozygotes. The FTO genotype explained 2% of the variance in adiposity changes. Our data suggest that the FTO obesity‐susceptibility genotype influences the body fat responses to regular exercise. Resistance to exercise‐induced reduction in total adiposity may represent one mechanism by which the FTO A allele promotes overweight and obesity.     

Body Fat and Fat‐Free Mass and All‐Cause Mortality

Objective: To investigate whether the association between BMI and all‐cause mortality could be disentangled into opposite effects of body fat and fat‐free mass (FFM). Research Methods and Procedures: All‐cause mortality was studied in the Danish follow‐up study “Diet, Cancer and Health” with 27, 178 men and 29, 875 women 50 to 64 years old recruited from 1993 to 1997. By the end of year 2001, the median follow‐up was 5.8 years, and 1851 had died. Body composition was assessed by bioelectrical impedance. Cox regression models were used to estimate the relationships among body fat mass index (body fat mass divided by height squared), FFM index (FFM divided by height squared), and mortality. All analyses were adjusted for smoking habits. Results: Men and women showed similar associations. J‐shaped associations were found between body fat mass index and mortality adjusted for FFM and smoking. The mortality rate ratios in the upper part of body fat mass were 1.12 per kg/m² (95% confidence interval: 1.07, 1.18) in men and 1.06 per kg/m² (95% confidence interval: 1.02, 1.10) in women. Reversed J‐shaped associations were found between FFM index and mortality with a tendency to level off for high values of FFM. Discussion: Our findings suggest that BMI represents joint but opposite associations of body fat and FFM with mortality. Both high body fat and low FFM are independent predictors of all‐cause mortality.     

Vastus medialis cross-sectional area is positively associated with patella cartilage and bone volumes in a pain-free community-based population

Introduction

Although vastus medialis and lateralis are important determinants of patellofemoral joint function, their relationship with patellofemoral joint structure is unknown. The aim of this study was to examine potential determinants of vastus medialis and lateralis cross-sectional areas and the relationship between the cross-sectional area and patella cartilage and bone volumes.

Methods

Two hundred ninety-seven healthy adult subjects had magnetic resonance imaging of their dominant knee. Vastus medialis and lateralis cross-sectional areas were measured 37.5 mm superior to the quadriceps tendon insertion at the proximal pole of the patella. Patella cartilage and bone volumes were measured from these images. Demographic data and participation in vigorous physical activity were assessed by questionnaire.

Results

The determinants of increased vastus medialis and lateralis cross-sectional areas were older age (P ≤ 0.002), male gender (P < 0.001), and greater body mass index (P ≤ 0.07). Participation in vigorous physical activity was positively associated with vastus medialis cross-sectional area (regression coefficient [beta] 90.0; 95% confidence interval [CI] 38.2, 141.7) (P < 0.001) but not with vastus lateralis cross-sectional area (beta 10.1; 95% CI -18.1, 38.3) (P = 0.48). The cross-sectional area of vastus medialis only was positively associated with patella cartilage volume (beta 0.6; 95% CI 0.23, 0.94) (P = 0.001) and bone volume (beta 3.0; 95% CI 1.40, 4.68) (P < 0.001) after adjustment for potential confounders.

Conclusions

Our results in a pain-free community-based population suggest that increased cross-sectional area of vastus medialis, which is associated with vigorous physical activity, and increased patella cartilage and bone volumes may benefit patellofemoral joint health and reduce the long-term risk of patellofemoral pathology.     

Gender Differences in Changes in Subcutaneous and Intra-abdominal Fat during Weight Reduction: An Ultrasound Study

WIRTH, ALFRED, AND BERIT STEINMETZ. Gender differences in changes in subcutaneous and intra-abdominal fat during weight reduction: an ultrasound study. Obes Res. 1998;6:393–399. Objective : In weight-reducing programs, men usually display greater improvement in metabolic risk factors than women. This gender difference may be related to enhanced weight and fat loss due to a greater energy deficit in men. To clarify the relationship between changes in metabolic profile, body fat composition, and weight loss, both sexes were studied under a regimen in which similar amounts of weight were lost. Research Methods and Procedures : A cross-sectional study using anthropometric (body mass index and waist-to-hip ratio), impedance (bioelectrical impedance analysis) and ultrasound measurement methods (thickness of subcutaneous fat layers, intra-abdominal sagittal diameter) were conducted. The metabolic risk profile was determined by measuring lipids, lipoproteins, and blood pressure. The weight loss program lasted 15 weeks: 3 weeks under controlled conditions in the hospital and 12 weeks on an ambulatory basis. Patients were instructed to follow a mixed diet. Calorie intake was restricted to 1500 kcal/day for the men and 1200 kcal/day for the women. Thirty-two subjects with obesity (16 men and 16 women), with a mean body mass index of 35 kg/m²—matched with regard to age, height, and body weight—took part in the study. Results : As expected, weight loss was similar for both sexes (?13.4 kg vs. ?12.8 kg). Also, body fat mass changed to the same extent in absolute and relative terms. The waist-to-hip ratio was identical before and after treatment in both sexes. The men lost more visceral fat than the women. This result is based on changes in intra-abdominal diameter as well as abdominal subcutaneous fat in relation to waist circumference. Changes in abdominal diameter were paralleled by reductions in triglycerides and increases in high-density lipoprotein-cholesterol. Subcutaneous fat loss was more pronounced in women than in men. Discussion : Where absolute and relative reductions in body weight and body fat are similar, men mobilize more intraabdominal fat than women, whereas women lose more subcutaneous fat. The greater reduction in intra-abdominal fat seen in men is accompanied by a more pronounced improvement in the metabolic risk profile. Therefore, greater improvement of risk factors in men is not only related to a greater negative energy balance, as shown in most studies, but is also sex-specific.     

The Implications of Body Fat Mass and Fat Distribution for Cognitive Function in Elderly Women

Objective: To investigate how body fat mass, an established source of endogenous estrogen after menopause, influences cognitive impairment in elderly women. Research Methods and Procedures: Study participants were 5607 generally healthy postmenopausal women with mean age of 63.8 years at baseline followed for an average of 7.3 years. Cognitive function assessed at follow‐up using the short Blessed test was related to baseline body weight, the yearly change in weight, and follow‐up measures of body fat depots assessed by DXA. Cognitive function was also related to various surrogates of lifetime estrogen exposure. Results: Women with the worst cognitive performance (score ≥ 9) at follow‐up were the ones who lost the most body weight and revealed the lowest central fat mass (CFM). The association of weight loss with worse cognitive performance was apparent across all age groups except for those more than 80 years old. In the multivariate logistic model, the risk of cognitive impairment was 18% lower in women in the second quartile of CFM (p = 0.14), 32% lower in the third (p = 0.01), and 48% lower in the fourth (p < 0.001) compared with those in the first quartile. CFM showed significant correlation with the simultaneously measured serum estradiol (r = 0.25; p < 0.001). Cognitive score showed an inverse linear relationship with the duration of reproductive period and bone mineral density assessed at follow‐up. Discussion: These findings argue for a protective association of body fat mass with cognitive impairment in elderly women. This association seems to involve a more prominent exposure to endogenous estrogens.     

Genetic Variation and Obesity in Australian Women: A Prospective Study

Objective: A number of candidate genes have been implicated in the pathogenesis of obesity in humans. This study examines associations between longitudinal changes in body mass and composition and the presence of polymorphisms in the β‐3 adrenergic receptor, tumor necrosis factor‐α, leptin, and leptin receptor (Lepr) in a cohort of Australian women. Research Methods and Procedures: Healthy white Australian women (n = 335) were randomly selected from the Barwon region of Victoria and underwent baseline anthropometry and double‐energy X‐ray absorptiometry for assessment of body mass and adiposity. These measurements were repeated again at 2‐year follow‐up. Genomic DNA was extracted and used for polymerase chain reaction‐based genotyping of all polymorphisms. Results: The Pro1019Pro Lepr polymorphism was associated with longitudinal increases in body weight (p = 0.02), fat mass (p = 0.05), and body mass index (p = 0.01) in this study, and individuals homozygous for the A allele at this locus had a greater propensity to gain body fat over time. The largest effects on body composition seemed to be in individuals already obese at baseline. Changes in body weight, fat mass, percent body fat, and body mass index over a 2‐year period were not associated with genetic variation in the β‐3 adrenergic receptor (Trp64Arg), tumor necrosis factor‐α promoter, or leptin genes in non‐obese or obese women. Discussion: These results suggest that a Lepr polymorphism is involved in the regulation of body mass and adiposity in obese Australian white women, which may have implications for the treatment of obesity in this population.     

Reverse causality and confounding and the associations of overweight and obesity with mortality

Objective: To examine the effect of reverse causality and confounding on the association of BMI with all‐cause and cause‐specific mortality. Research Methods and Procedures: Data from two large prospective studies were used. One (a community‐based cohort) included 8327 women and 7017 men who resided in two Scottish towns at the time of the baseline assessment in 1972–1976; the other (an occupational cohort) included 4016 men working in the central belt of Scotland at the time of the baseline assessment in 1970–1973. Participants in both cohorts were ages 45 to 64 years at baseline; the follow‐up period was 28 to 34 years. Results: In age‐adjusted analyses that did not take account of reverse causality or smoking, there was no association between being overweight (BMI 25 to <30 kg/m²) and mortality, and weak to modest associations between obesity (BMI ≥30 kg/m²) and mortality. There was a strong association between smoking and lower BMI in women and men in both cohorts (all p < 0.0001). Among never‐smokers and with the first 5 years of deaths removed, overweight was associated with an increase in all‐cause mortality (relative risk ranging from 1.12 to 1.38), and obesity was associated with a doubling of risk in men in both cohorts (relative risk, 2.10 and 1.96, respectively) and a 60% increase in women (relative risk, 1.56). In both never‐smokers and current smokers, being overweight or obese was associated with important increases in the risk of cardiovascular disease. Discussion: These findings demonstrate that with appropriate control for smoking and reverse causality, both overweight and obesity are associated with important increases in all‐cause and cause‐specific mortality, and in particular with cardiovascular disease mortality.     

The effect of pioglitazone and resistance training on body composition in older men and women undergoing hypocaloric weight loss

Age‐related increases in ectopic fat accumulation are associated with greater risk for metabolic and cardiovascular diseases, and physical disability. Reducing skeletal muscle fat and preserving lean tissue are associated with improved physical function in older adults. PPARγ‐agonist treatment decreases abdominal visceral adipose tissue (VAT) and resistance training preserves lean tissue, but their effect on ectopic fat depots in nondiabetic overweight adults is unclear. We examined the influence of pioglitazone and resistance training on body composition in older (65–79 years) nondiabetic overweight/obese men (n = 48, BMI = 32.3 ± 3.8 kg/m²) and women (n = 40, BMI = 33.3 ± 4.9 kg/m²) during weight loss. All participants underwent a 16‐week hypocaloric weight‐loss program and were randomized to receive pioglitazone (30 mg/day) or no pioglitazone with or without resistance training, following a 2 × 2 factorial design. Regional body composition was measured at baseline and follow‐up using computed tomography (CT). Lean mass was measured using dual X‐ray absorptiometry. Men lost 6.6% and women lost 6.5% of initial body mass. The percent of fat loss varied across individual compartments. Men who were given pioglitazone lost more visceral abdominal fat than men who were not given pioglitazone (?1,160 vs. ?647 cm³, P = 0.007). Women who were given pioglitazone lost less thigh subcutaneous fat (?104 vs. ?298 cm³, P = 0.002). Pioglitazone did not affect any other outcomes. Resistance training diminished thigh muscle loss in men and women (resistance training vs. no resistance training men: ?43 vs. ?88 cm³, P = 0.005; women: ?34 vs. ?59 cm³, P = 0.04). In overweight/obese older men undergoing weight loss, pioglitazone increased visceral fat loss and resistance training reduced skeletal muscle loss. Additional studies are needed to clarify the observed gender differences and evaluate how these changes in body composition influence functional status.     

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.     

Excess Weight and the Risk of Incident Coronary Heart Disease Among Men and Women

Overweight and obesity have been prospectively associated with the risk of coronary heart disease (CHD). Less clear is the relation of excess weight to risk of CHD among men and women with comorbid conditions, and the proportion of CHD risk attributable to excess weight in the US population. To assess the risk of CHD associated with excess weight among men and women with and without associated comorbid conditions, and determine the population attributable risk of CHD associated with excess weight. The study population consisted of two prospective cohorts, the Health Professionals Follow‐up Study (HPFS) (N = 42,351 men; age range at baseline, 39–75 years) and the Nurses' Health Study (NHS) (N = 76,703 women; age range at baseline, 39–65 years). A total of 2,771 incident cases of CHD among the men and 2,359 among the women were documented over the 16 years of follow‐up. Overall, the relative risk (RR) of CHD associated with BMI ≥30 kg/m² compared with BMI 18.5–22.9 kg/m² was 2.13 (95% confidence interval (CI), 1.82–2.48) among the men and 2.48 (95% CI, 2.20–2.80) among the women. The risk of CHD increased with BMI, both with and without the presence of comorbid conditions. Our estimates suggest that more than a third of all incident CHD in US men and women may be attributed to excess weight. Excess weight is associated with increased risk of CHD among men and women, both alone and in combination with comorbid conditions, though the results require careful interpretation. A substantial proportion of incident CHD may be attributed to excess weight.     

Does an increase in body mass index over 10 years affect knee structure in a population-based cohort study of adult women?

Introduction  

Although obesity is a modifiable risk factor for knee osteoarthritis (OA), the effect of weight gain on knee structure in young and healthy adults has not been examined. The aim of this study was to examine the relationship between body mass index (BMI), and change in BMI over the preceding 10-year period, and knee structure (cartilage defects, cartilage volume and bone marrow lesions (BMLs)) in a population-based sample of young to middle-aged females.     

Low Resting and Sleeping Energy Expenditure and Fat Use Do Not Contribute to Obesity in Women

Objective: Determine whether sleeping and resting energy expenditure and sleeping, resting, and 24‐hour fuel use distinguish obesity‐prone from obesity‐resistant women and whether these metabolic factors explain long‐term weight gain. Research Methods and Procedures: Forty‐nine previously overweight but currently normal‐weight women were compared with 49 never‐overweight controls. To date, 87% of the 98 women have been re‐evaluated after 1 year of follow‐up, without intervention, and 38% after 2 years. Subjects were studied at a General Clinical Research Center after 4 weeks of tightly controlled conditions of energy balance and macronutrient intake. Forty‐nine obesity‐prone weight‐reduced women were group‐matched with 49 never‐overweight obesity‐resistant controls. All were premenopausal, sedentary, and normoglycemic. Energy expenditure and fuel use were assessed using chamber calorimetry. Body composition was assessed using DXA. Results: At baseline, percent body fat was not different between the obesity‐prone and control women (33 ± 4% vs. 32 ± 5%, respectively; p = 0.22). Analysis of covariance results show that after adjusting for lean and fat mass, sleeping and resting energy expenditure of obesity‐prone women was within 2% of controls. Neither sleeping nor resting energy expenditure nor sleeping, resting, or 24‐hour fuel use was significantly different between the groups (p > 0.25). None of the metabolic variables contributed significantly to patterns of weight gain at 1 or 2 years of follow‐up. Discussion: The results suggest that when resting and sleeping energy expenditure and fuel use are assessed under tightly controlled conditions, these metabolic factors do not distinguish obesity‐prone from obesity‐resistant women or explain long‐term weight changes.     

Relationship of Body Composition to Body‐Fatness Estimation in Japanese University Students

Objective: To examine the relationship between self‐estimated whole body size and fatness and whole body and regional composition, and the relationship between self‐estimated whole body fatness and self‐estimated regional fatness in Japanese university students. Research Methods and Procedures: This was a cross‐sectional study using Japanese university students (110 men and 79 women). The percentage of body fat, fat mass (FM), and fat‐free mass (FFM) were measured by underwater weighing and used as body composition variables. Subcutaneous fat thicknesses were determined at seven sites by ultrasonography to estimate regional body composition, and six circumferences and four breadths to estimate regional size. Relative body size and fatness were self‐estimated using a questionnaire. Results: Only women tended to estimate themselves as being fatter than they actually were. Self‐estimated body fatness moderately correlated with the percentage of body fat (men, r = 0.41; women, r = 0.40) FM (men, r = 0.50; women, r = 0.51), and body mass index (r = 0.56 for men and 0.56 for women). After adjusting for the percentages of body fat and FM, self‐estimated fatness correlated with body mass index (r = 0.31 for men and r = 0.37 for women). Among self‐estimated regional fatness, self‐estimated abdominal fatness had the strongest correlation with self‐estimated whole body fatness in both genders. Discussion: The low correlation between estimated and actual body fatness in both genders indicates that Japanese university students, especially women, inaccurately estimate their percentage of body fat. In fact, both men and women primarily estimate their whole body fatness by body weight relative to height.     

The Canadian Obesity Epidemic: An Historical Perspective

Objective: To examine temporal trends in stature, body mass, body mass index (BMI), and the prevalence of overweight and obesity in Canada. Research Methods and Procedures: Data for adults 20 to 64 years of age were compared across eight Canadian surveys conducted between 1953 and 1998. Temporal trends in stature and body mass were examined using regression, and changes in weight‐for‐height were expressed as changes from 1953. BMI data were available from 1970 to 1972 to examine changes in overweight and obesity. Qualitative changes in the BMI distribution were examined using Tukey mean‐difference plots. Results: Significant temporal trends in stature and body mass have occurred since 1953 in Canada. Median stature increased 1.4 cm/decade in men and 1.1 cm/decade in women, whereas median body mass increased 1.9 kg/decade in men and 0.8 kg/decade in women. Increases in the 75th percentile of body mass were larger than the median. The average weight‐for‐height increased 5.1% in men and 4.9% in women from 1953. Furthermore, the prevalences of overweight and obesity have increased from 40.0% and 9.7% in 1970–1972 to 50.7% and 14.9% in 1998, respectively. The entire BMI distribution has shifted to the right since 1970–1972 and has become more skewed to the right for men than for women. Discussion: There have been significant increases in stature and body mass in Canada over the last 45 years. Body mass has increased more than stature, particularly in the upper percentiles, which has resulted in the currently observed high prevalences of overweight and obesity.     

Differences in Resting Metabolic Rate between White and African‐American Young Adults

Objective: A reported lower resting metabolic rate (RMR) in African‐American women than in white women could explain the higher prevalence of obesity in the former group. Little information is available on RMR in African‐American men. Research Methods and Procedures: We assessed RMR by indirect calorimetry and body composition by DXA in 395 adults ages 28 to 40 years (100 African‐American men, 95 white men, 94 African‐American women, and 106 white women), recruited from participants in the Coronary Artery Risk Development in Young Adults (CARDIA), Birmingham, Alabama, and Oakland, California, field centers. Results: Using linear models, fat‐free mass, fat mass, visceral fat, and age were significantly related to RMR, but the usual level of physical activity was not. After adjustment for these variables, mean RMR was significantly higher in whites (1665.07 ± 10.78 kcal/d) than in African Americans (1585.05 ± 11.02 kcal/d) by 80 ± 16 kcal/d (p < 0.0001). The ethnic × gender interaction was not significant (p = 0.9512), indicating that the difference in RMR between African‐American and white subjects was similar for men and women. Discussion: RMR is ～5% higher in white than in African‐American participants in CARDIA. The difference was the same for men and women and for lean and obese individuals. The prevalence of obesity is not higher in African‐American men than in white men. Because of these reasons, we believe that RMR differences are unlikely to be a primary explanation for why African‐American women are more prone to obesity than white women.