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Exercise is frequently identified as a predictor of weight maintenance after elective weight loss in retrospective studies of treatments for obesity. We conducted a prospective study to test whether physical activity measured soon after weight loss predicted weight maintenance and to determine how much physical activity was required to optimize maintenance. Thirty-two women [mean (+/- SD) age, 38 +/- 7 y; body mass index (in kg/m2), 24 +/- 3] were recruited through local advertising within 3 mo of reaching their target for weight loss (23 +/- 9 kg). Total energy expenditure (TEE) was measured by the doubly labeled water method. Postabsorptive resting metabolic rate (RMR) and postprandial RMR [expressed as thermic effect of a meal (TEM)] were measured by respiratory gas exchange. Women in the physically active group (ratio of TEE to RMR = 1.89 +/- 0.08) gained 2.5 +/- 3.1 kg during the 12 mo after reaching their target for weight loss, moderately active women (TEE:RMR = 1.64 +/- 0.05) gained 9.9 +/- 10.5 kg, and sedentary women (TEE:RMR = 1.44 +/- 0.08) gained 7.0 +/- 5.9 kg (P < 0.01). Retrospective analyses of weight regain as a function of energy expended in physical activity indicated a threshold for weight maintenance of 47 kJ x kg body wt(-1) x d(-1). This corresponds to an average of 80 min/d of moderate activity or 35 min/d of vigorous activity added to a sedentary lifestyle.

Standardization of measurement conditions is essential for obtaining accurate, precise, and reproducible bioelectrical impedance analysis (BIA) data. Errors due to lack of measurement control are propagated in subsequent calculations of body composition and contribute to differences in predictive equations among investigators. Various individual and environmental factors have been shown to influence BIA. We review the factors that have been identified from the literature as being conditions requiring standardization both for healthy subjects and for those in a medical setting.

The use of bioelectrical impedance analysis (BIA) in patients with end-stage renal disease who are receiving dialysis provides researchers with two important applications: 1) a biological model in which the underlying assumptions of BIA can be tested, and 2) if valid, a tool that can be used to improve the clinical management of patients receiving dialysis. We review the rationale of and purpose for using BIA in the dialysis population, the physiologic changes that occur during dialysis that influence BIA measurements, and last, conclusions reached from the current scientific literature.

Several recent self-reported surveys have suggested that African-American women may engage in less leisure-time physical activity (PA) than whites. Objective measurements of PA have not been performed, however. Therefore, the purpose of this study was to compare the components of energy expenditure, including PA, between black and white obese women. Using the doubly labeled water method, total daily energy expenditure (TDEE), basal metabolic rate (BMR), thermic effect of a meal (TEM), and PA were measured in 14 black and 15 white moderately obese women over 2 weeks. No statistically significant differences were seen between the 2 groups in BMR, TEM or TDEE. Mean PA was significantly (p = 0.05) lower among black women compared to whites when expressed as MJ. d-1 (3.49 vs. 4.30) or kJ.kg-1.d-1 (37.6 vs. 47.7). Our study supports the survey differences seen in PA among black and white women.

Comparison of heart rate and physical activity recall with doubly labeled water in obese women. Med. Sci. Sports Exerc., Vol. 27, No. 1, pp. 126-133, 1995. Accurate methods of estimating total daily energy expenditure (TDEE) that are inexpensive and differentiate activities of varying intensities are needed in obesity research. We compared minute-by-minute heart rate (HR) monitoring and the 7-d physical activity recall (PAR) questionnaire with doubly labeled water (DLW) for the measurement of TDEE and physical activity in 14 obese women (45% +/- 4% fat, mean +/- SD) before and during 12 wk of weight reduction. TDEE was measured over 2 wk by DLW. HR monitoring was conducted for 3 d, with individual VO2/HR calibrations applied to HR data above 3 METs. PAR revealed the amount of time spent in sleep, moderate, hard, and very hard activities during 1 wk, with time spent in light activities determined by difference. Mean TDEE values, expressed as the % difference from DLW, prior to weight loss were -5.2 +/- 10.8% by HR and 3.4 +/- 14.4 by PAR, and during the diet were + 0.9 +/- 14.1% by HR and + 0.9 +/- 14.7% by PAR. Individual variability was high for both HR (-24.0 to + 25.6%) and PAR (-27.4 to + 36.2%). Energy expended in physical activity prior to weight loss were 3.97 +/- 1.23 MJ.d-1 by DLW, 3.91 +/- 0.90 by HR, and 4.79 +/- 0.95 by PAR. During weight loss, physical activity values by DLW, HR, and PAR were 4.31 +/- 1.18, 4.84 +/- 2.22, and 4.64 +/- 1.06 MJ.d-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)