Search

Background: Little is known about the effect of weight change on regional lean body mass (LBM) distribution or on racial differences in resting metabolic rate (RMR). Objective: The study compared total and regional LBM patterns in white and black women after weight loss and regain and assessed the influence of regional LBM on variances in RMR. Design: Eighteen white and 22 black women who did not differ in age, weight, and height were studied 3 times: in the overweight state, after weight reduction to the normal-weight state, and after 1 y without intervention. Total and regional lean and fat masses were assessed by dual-energy X-ray absorptiometry. Results: White and black women did not differ significantly in mean ([+ or -] SD) weight loss (13.4 [+ or -] 3.6 and 12.7 [+ or -] 3.2 kg, respectively) and regain (6.1 [+ or -] 5.5 and 6.4 [+ or -] 5.4 kg, respectively). Black subjects had significantly less trunk LBM and significantly more limb LBM at each time point (P < 0.05). In both races, weight regain was associated with significant increases in limb LBM (P < 0.05) but not in trunk LBM (P = 0.21). RMR, adjusted for total LBM and fat mass, was significantly higher in white women after weight loss (P < 0.01) and regain (P < 0.01). However, no racial difference was found when RMR was adjusted for LBM distribution. Conclusions: In both races, trunk LBM decreased with weight loss and remained lower, despite significant weight regain, which potentially reflected decreased organ mass. Regional LBM distribution explained the racial difference in RMR. KEY WORDS Overweight, obesity, weight loss, body composition, resting metabolic rate, lean body mass, fat mass, regional distribution, African American women

Background: Few studies have tested the hypothesis that changes in disease risk factors are more closely associated with changes in visceral fat than with changes in other adipose tissue depots, particularly in subjects with different ethnic or racial backgrounds. Objective: We describe changes in triacylglycerol, total cholesterol, HDL cholesterol, LDL cholesterol, insulin sensitivity ([S.sub.i]), visceral fat, and subcutaneous abdominal adipose tissue (SAAT) with weight loss in premenopausal, overweight [body mass index (in kg/[m.sup.2]): 27-30], African American (n = 19) and white (n = 18) women. Design: Assessments were performed before and after diet-induced weight loss to a BMI < 25. Body composition and body fat distribution were assessed with dual-energy X-ray absorptiometry and computed tomography, respectively; [S.sub.i] was assessed with an intravenous-glucose-tolerance test and minimal modeling. Results: White women lost significantly more visceral fat and less SAAT than did African American women despite similar weight losses ([approximately equal to] 13 kg). Mixed-model analysis indicated significant effects of time (ie, weight loss) on [S.sub.i], triacylglycerol, HDL cholesterol, and LDL cholesterol and of race on triacylglycerol. Time race interaction terms were not significant. After adjustment for either total body or visceral fat, time was not related to any outcome variable; however, race remained significantly related to triacylglycerol. Conclusions: With weight loss, moderately overweight African American and white women experienced significant improvements in [S.sub.i] and lipids. The beneficial effects of weight loss did not differ with race and could not be attributed to a specific body fat depot. Lower triacylglycerol concentrations among African American women are independent of both obesity status and body fat distribution. KEY WORDS Body fat distribution, intraabdominal fat, weight loss, insulin sensitivity, cholesterol, triacylglycerol, African American women, white women

Background: Black women are at greater risk of obesity than are white women, perhaps because of their lower levels of physical activity. Objective: We compared free-living activity energy expenditure (AEE) in sedentary white and black women (in overweight and normal-weight states) and in never-overweight control subjects. Design: Subjects included 46 women (23 white, 23 black) studied while overweight and after reaching a normal weight and 38 female control subjects (23 white, 15 black). Diet, without exercise training, resulted in a mean weight loss of 13 kg and a body mass index (in kg/[m.sup.2]) Results: No significant racial differences in body composition, before or after weight loss, were found. After weight loss, AEE and aerobic capacity increased in the white women and decreased in the black women (P < 0.05 and P < 0.02, respectively). After weight loss, but not before, the white women had a significantly higher mean AEE than did the black women (2448 [+ or -] 979 and 1728 [+ or -] 1373 kJ/d, respectively; P < 0.05), approximating AEEs in the white (2314 [+ or -] 105) and black (2310 [+ or -] 1251) control subjects. Conclusions: Relative to the responses of the white women to diet-induced weight loss, the black women became less fit and less physically active. Induction of a normal body weight in overweight black women appeared to produce a more obesity-prone state, favoring weight relapse. KEY WORDS Overweight, obesity, weight loss, body composition, energy expenditure, energy economy, physical activity, exercise, African American women

Background: Although physical inactivity is believed to contribute to the rising prevalence of obesity, the role and magnitude of its contribution to weight gain are unknown. Objective: We compared total free-living activity energy expenditure (AEE) and physical activity level in women successful and unsuccessful at maintaining a normal body weight. Design: Premenopausal, generally sedentary women were studied at their normal weight and 1 y later after no intervention. Two groups were identified on the basis of extreme weight changes: maintainers (n = 27) had a weight gain of [less than or equal to] 3% of their initial body weight ([less than or equal to] 2 kg/y) and gainers (n = 20) had a weight gain of > 10% (>6 kg/y). At baseline and follow-up, evaluations were conducted during 4 wk of diet-controlled, energy-balance conditions. Free-living AEE and physical activity were assessed with the use of doubly labeled water, exercise energy economy and muscle strength with the use of standardized exercise tests, and sleeping EE and substrate utilization with the use of chamber calorimetry. Results: Maintainers lost a mean ([+ or -]SD) of 0.5 [+ or -] 2.2 kg/y and gainers gained 9.5 [+ or -] 2.1 kg/y. Gainers had a lower AEE (P < 0.02), a lower physical activity level (P < 0.01), and less muscle strength (P < 0.001); these differences between groups remained significant from baseline to follow-up. Sleeping EE, exercise economy, and sleeping or 24-h substrate utilization were not significantly different between the 2 groups. A lower AEE in the gainers explained [approxiamately equal to] 77% of their greater weight gain after 1 y. Conclusion: The general US population should increase their daily physical activity levels to decrease the rising prevalence of obesity. Am J Clin Nutr 2002;75:499-504. KEY WORDS Weight gain, obesity, physical activity, energy expenditure, muscle strength, fitness, premenopausal women

Research reveals differences in maximal oxygen uptake between African-American and Caucasian women and this variation persists even after adjusting for hemoglobin levels, muscle activity, and leg lean tissue volume. Data indicate that all three criteria are lower for African-American women than in Caucasian women.

Treadmill measures and criteria to determine VO(sub.2max) in prepubertal girls and their reliability have been investigated. The study also was intended to find the percentage of young females able to achieve VO(sub.2max) and to describe methods that would allow a high proportion of young persons to get to that point. It was found that exercise measurements using treadmill testing were reliable for healthy, prepubertal girls of normal weight. Older girls, when compared to the younger, were able to achieve VO(sub.2max) more often. One testing should give an accurate measure of walking efficiency and aerobic capacity. Two criteria are sufficient for determining VO(sub.2max)

Three major factors modulate body weight: metabolic factors, diet, and physical activity, each influenced by genetic traits. Despite recent advances in these areas, the prevalence of obesity in Westernized societies has increased. In contrast to monogenic animal models and rare human genetic syndromes, predisposition to common forms of obesity is probably influenced by numerous susceptibility genes, accounting for variations in energy requirements, fuel utilization, muscle metabolic characteristics, and taste preferences. Although recent increases in obesity prevalence cannot be explained by changes in the gene pool, previously 'silent' genetic variants may now play important permissive roles in modern societies. Available data suggest that variations in resting energy expenditure, thermic effect of food, and fuel utilization exist but, by themselves, are unlikely to explain the onset of obesity. Regarding diet, the best available trend survey data indicate that fat and energy intake have fallen, in this and other Westernized countries. Diverging trends of decreasing energy intake and increasing body weight suggest that reduced physical activity may be the most important current factor explaining the rising prevalence of obesity. Subsistence in modern societies requires extreme adaptations in previously useful energy-conserving diet and exercise behaviors. Recognizing the difficulties in sustaining energy-restricted diets in the presence of fast foods and social feasts, the current trend toward increasing body weight is not likely to be reversed solely through recommendations for further reductions in energy intake. In all likelihood, activity levels will have to increase in response to an environment engineered to be more physically demanding. Am J Med. 1998;105:145-150. [C] 1998 by Excerpta Medica, Inc.

PURPOSE: To compare recent changes in diet and physical activity with trends in body weight and obesity prevalence, using large survey studies representative of the US population. MATERIALS AND METHODS: Secular-trends survey studies were made from databases of NHANES 11 and III, USDA Nationwide Food Consumption Survey, Behavioral Risk Factor Survey System, and Calorie Control Council Report providing data on obesity prevalence, body mass index, calorie and fat intake, exercise-related physical activity, and consumption of low-calorie food extracted from surveys for the adult US population and specific subgroups. RESULTS: In the adult US population the prevalence of overweight rose from 25.4% from 1976 to 1980 to 33.3% from 1988 to 1991, a 31% increase. During the same period, average fat intake, adjusted for total calories, dropped from 41.0% to 36.6%, an 11% decrease. Average total daily calorie intake also tended to decrease, from 1,854 kcal to 1,785 kcal (-4%). Men and women had similar trends. Concurrently, there was a dramatic rise in the percentage of the US population consuming low-calorie products, from 19% of the population in 1978 to 76% in 1991. From 1986 to 1991 the prevalence of sedentary lifestyle represented almost 60% of the US population, with no change over time. CONCLUSIONS: Reduced fat and calorie intake and frequent use of low-calorie food products have been associated with a paradoxical increase in the prevalence of obesity. These diverging trends suggest that there has been a dramatic decrease in total physical activity related energy expenditure. Efforts to increase the average American's total exercise- and nonexercise-related physical activities may be essential for the prevention of obesity. Am J Med. 1997;102:259-264. [C] 1997 by Excerpta Medica, Inc.

We examined the pattern of weight maintenance in 24 obese women [body mass index (BMI; in kg/m2) 27.6 [+ or -] 0.4 who were provided foods for a balanced deficit diet until each had lost [greater than or equal to] 10 kg and attained normal body weight (BMI 22.9 [+ or -] 0.4). At I y subjects had regained a mean of 42% of their weight loss, which increased to 87% at 4 y. At 4 y 44% of patients had regained < 75%, whereas 37% had regained [less than or equal to]100% of the weight originally lost. The amount of weight gained was markedly different from that observed in 24 pair-matched never-obese control subjects over the same length of follow-up. Because the results reported herein were obtained without teaching the subjects weight-control skills, they may be regarded as reflective of the natural history of weight maintenance in this population and may serve as a reference for various weight-intervention programs. The pattern of weight rebound observed in this study is very similar to the pattern observed in combined results from published diet and behavioral-modification Programs, which raises important questions regarding the efficacy of these approaches in long-term weight maintenance.

The purpose of this study was to determine the effects of a nutrition-education program provided by a physician nutrition specialist in a family-practice residency program on residents' and faculty members' nutrition knowledge and nutrition-related patient care, their patients' perceptions of the importance of nutrition, and the physicians' dietary patterns. The nutrition specialist provided recommendations for nutrition patient-care practices to the physicians for 6 mo. Pre- and post-intervention assessments included 1) nutrition exams for physicians and patients, 2) patient questionnaires concerning attitudes towards nutrition, 3) chart reviews, and 4) diet records for physicians. The educational intervention caused a small but statistically significant (P < 0.01) increase in physicians' nutrition-knowledge scores and a significantly higher (P < 0.05) frequency of physicians discussing nutrition and recommending diets for their patients. Effects were greater among residents than among faculty members. The results suggest that a physician nutrition specialist can provide effective nutrition education within a residency program.

On the basis of literature values, the relationship between fat-free mass (FFM), fat mass (FM), and resting energy expenditure [REE (kJ/24 h)] was determined for 213 adults (86 males, 127 females). The objectives were to develop a mathematical model to predict REE based on body composition and to evaluate the contribution of FFM and FM to REE. The following regression equations were derived: 1) REE = 1265 + (93.3 X FFM) ([r.sup.2] = 0.727, P < 0.001); 2) REE = 114 + (90.4 X FFM) + (I 3.2 X FM) ([R.sup.2] = 0.743, P < 0.001); and 3) REE = (108 X FFM) + (16.9 X FM) ([R.sup.2] = 0.986, P < 0.001). FM explained only a small part of the variation remaining after FFM was accounted for. The models that include both FFM and FM are useful in examination of the changes in REE that occur with a change in both the FFM and FM. To account for more of the variability in REE, FFM will have to be divided into organ mass and skeletal muscle mass in future analyses. Am J Clin Nutr 1992;56:848-56.

The separate effects of energy restriction and weight loss on serum lipids were studied in 24 postmenopausal moderately obese women before and after weight loss of > 10 kg to normal weight. Fasting serum triglycerides (TGs), total cholesterol (TC), high-density-lipoprotein (HDL) and low-density-lipoprotein (LDL) cholesterol, and insulin were measured a the end of four 10-d in-hospital phases, two before and two after weight loss: phase I, stable weight; phase II, 3350 kJ/d (800 kcal/d). followed by outpatient weight loss; phase III, 3350 kJ/ d (800 kcal/d); and phase IV, stable weight. Diet composition and exercise were constant the entire study. Energy-restriction effect was determined by comparing average values in stable-weight phases (I and IV) with low-energy phases (II and III); weight-loss effect was determined by comparing values in obese phases (I and II) with reduced-weight phases (III and IV). Energy restriction lowered TG, TC, LDL cholesterol, the LDL-HDL cholesterol ratio, and insulin and raised HDL cholesterol (all P < 0.05). Weight loss lowered TG, TC, LDL cholesterol, and insulin (all P < 0.01) but did not change HDL cholesterol or the LDL-HDL cholesterol ratio. The results suggest that reduction to a weight-steady nonobese state significantly lowers TG, TC, and LDL cholesterol but does not improve HDL cholesterol or the LDL-HDL cholesterol ratio. Am J Clin Nutr 1992; 56:44-9.

It is not known whether the decrease in the thermic effect of food (TEF) in obesity is a consequence of obesity or a factor contributing to the development of obesity. The resting energy expenditure (REE) of 24 obese, nondiabetic, postmenopausal women was 5481 [+ or -] 110 kJ/24 h (1310 [+ or -] 26.4 kcal/24 h). After weights loss (12.7 [+ or -] 0.45 kg) the REE was significantly decreased (4858 [+ or -] 94 kJ/24 h, or 1161 [+ or -] 22.4 kcal/24 h) and equivalent to the REE of 4866 [+ or -] 119 kJ/24 h (1163 [+ or -] 28.5 kcal/24 h) in 24 never-obese, postmenopausal women. The TEF, expressed as a percentage of the calories ingested, was 8.2 [+ or -] 0.05% for obese subjects, 8.7 [+ or -] 0.57% for postobese subjects, and 9.8 [+ or -] 0.54% for never-obese subjects. Compared with never-obese subjects, the TEF was significantly reduced in obese subjects (P = 0.043) and remained unchanged after weight loss (P = 0.341). These findings indicate that the lower TEF in the obese subjects is uncorrected by weight loss, and thus it is a contributor to obesity rather than a consequence of obesity.

Two studies were performed to investigate the association between body fat mass and fat oxidation. The first, a cross-sectional study of 106 obese women maintaining stable body weight, showed that these two variables were significantly correlated (r = 0.56, P < 0.001) and the regression coefficient indicated that a 10-kg change in fat mass corresponded to a change in fat oxidation of 20 g/d. The second, a prospective study, validated this estimate and quantifies the long-term adaptations in fat oxidation resulting from body fat loss. Twenty-four moderately obese women were studied under controlled dietary conditions at stable weight before and after mean weight and fat losses of 12.7 and 9.8 kg, respectively. The reduction in fat oxidation was identical to that predicted by the above regression. We conclude that changes in fat mass significantly affect fat oxidation and that this process may contribute to the long-term regulation of fat and energy balance in obese individuals.

Even though it is clear that proper nutrition plays an important role in maintaining health and preventing disease, many residents and practicing physicians have had limited training in clinical nutrition. A study was performed to identify the important features of clinical nutrition programs that have proven to be the most effective for teaching nutrition to residents. To accomplish this task, 238 nutrition educators and 787 residency-program directors were asked to identify the top nutrition programs in the country. Surveys were conducted at 23 institutions with the best programs, and seven of these institutions were visited. The results of the survey indicate that the key element to successful training of residents in clinical nutrition is the presence of an active physician-nutritionist role model. It is important to have a physician who is actively involved in patient care assume a leadership role as a nutrition expert to emphasize the nutritional aspects of disease. The second most important feature is a multidisciplinary nutrition-support team to provide education for the residents. Clinical rotations or electives in nutrition are an important part of the training experience. The curriculum should include lectures and conferences in addition to clinical activities that allow the residents to have first-hand experience with patients. A strong academic environment is important for attracting topnotch faculty. (Consumer Summary produced by Reliance Medical Information, Inc.)

PURPOSE: Although weight reduction generally lowers blood pressure, it is unclear whether the resPOnse is due to concurrent dietary changes or to reduced body mass itself. in this study, the independent effects of energy restriction and weight reduction were examined prospectively in 24 obese, hypertensive, normoglycemic women whose dietary intake was tightly controlled. SUBJECTS AND METHODS: Sodium, potassium, and calcium intake, the polyunsaturated/saturated fat ratio, and the proportional composition of carbohydrate, fat, and protein were constant throughout the 5-month protocol. Hemodynamic and neuroendocrine status was evaluated in four 10-day hospital phases.- two prior to weight loss (energy balance and then 800-kcal intake), and two after an average loss of 13 kg to normal body weight (800 kcal and then return to energy balance). RESULTS: Fasting serum insulin, trilodothyronine inreverse trilodothyronine ratio, resting metabolic rate, and heart rate declined, and sodium and potassium balances were negative during energy restriction. Catecholamines, renin, aldosterone, plasma volume, cardiac output, and blood pressure showed no consistent response to changes in energy intake. By contrast, weight reduction independently lowered blood pressure, plasma volume, cardiac output, and plasma renin activity. Body fat pattern remained unchanged. CONCLUSION: These results demonstrate that weight loss has a blood pressure-lowering effect that is distinct from energy restriction and that is related to changes in blood volume and cardiac output., Evidence exists that people who are overweight are more prone to high blood pressure. When patients are placed on restricted diets to lose weight, blood pressure also decreases. Three factors involved in dieting may account for these decreases: lower caloric intake, reduced sodium intake, and decreased body fat content. No study has conclusively shown that any of the decrease in blood pressure is attributable to the decreased body fat alone rather than to the caloric and sodium restrictions. This study examined the separate effects of caloric restriction and decreased body fat on lowering blood pressure. The study followed 24 women who were mildly obese and had mild to moderate hypertension (high blood pressure). The women were placed on a restricted-calorie diet to decrease body fat, but were given constant levels of sodium and other nutrients, as well as carefully proportioned diets, to eliminate other factors from contributing to decreased blood pressures. Once the women had reached a nearly normal weight, caloric content was increased to a maintenance level to factor out caloric restriction in blood pressure results. The subjects lost an average of 17 percent of their body weight during the study. Blood pressures in the subjects were significantly lower at the end of the study than at its beginning. Analysis of blood pressure data taken throughout the study revealed that decreases in blood pressure were statistically related to decreased body fat, but not to caloric restriction. Metabolic measurements of insulin and other substances followed the pattern expected for caloric restriction, but did not closely correlate with blood pressure. Thus, blood pressure decreases seen in subjects who restrict calories are not only a short-term effect of caloric deprivation, but also an effect of body fat reduction. (Consumer Summary produced by Reliance Medical Information, Inc.)

OBJECTIVE: Currently recommended rates of weight loss for obese persons are not based on demonstrated health risks. The authors attempt to determine a medically safe rate of weight loss based on currently available data on the risk of gallstone formation during active weight loss. METHODS: All prospective studies published in the English language on the formation of gallstones in obese persons during active weight loss were reviewed and evaluated. A statistical analysis was performed using studies of at least 4 weeks' duration that included information on diet composition, rates of weight loss, length of follow-up, and incidence of gallstone formation. A statistical model was fit to the data from the studies that met the criteria. RESULTS: Nine subject groups derived from five published reports met the criteria for inclusion in the analysis. When the results of these groups were evaluated statistically, a curvilinear relationship between incidence of gallstone formation and rate of weight loss was demonstrated. The relationship was best described by an exponential regression curve, with an adjusted [r.sup.2] of 0.98 and a dramatically increasing risk of gallstone formation at rates of weight loss above 1.5 kg per week. CONCLUSION: Risk of gallstone formation in obese persons during active weight loss seems to increase in an exponential fashion. The data suggest that rates of weight loss should not exceed an average of 1.5 kg per week.