The short-term effect of a balanced defecit diet on resting energy expenditure in overweight and obese males and females.

There is variability in the pattern of weight change in response to a weight loss intervention (i.e., slowing of subsequent weight loss, cessation of weight loss, weight regain). A reduction in resting energy expenditure (REE) may partially explain the observed variability. Few studies have examined the effect of initial weight loss on change in REE. PURPOSE: To examine the change in REE in response to weight loss across a 4-week period in overweight and obese males and females. METHODS: Thirty-seven subjects (body mass index 25.0-39.9 kg/m2; males = 14, females = 23) participated in a 4-week intervention with random assignment to an Experimental Group or a no treatment Control Group. The experimental group was instructed to reduce energy intake to 1200-1500 kcal/d and participate in 100 min/wk of moderate aerobic exercise. The control group was instructed to maintain current eating and exercise behaviors. Assessments of body weight, body composition, and REE were conducted at 0 and 4 weeks. REE was expressed as absolute REE (kcal/d), REE relative to body weight, (kcal/kg/d), REE relative to lean body mass (kcal/kgLBM/d). RESULTS: Thirty-five subjects completed the study (94.6%). There were significant differences (p<0.05) for change in outcomes between the experimental and control groups for body weight (-3.3+1.7 vs. 0.6+1.1 kg) lean body mass (-0.6+0.9 vs. 0.2+0.9 kg), absolute REE (-205.8+193.0 vs. -11.4+ 140.6 kcal/d), and REE relative to lean body mass (-3.3+2.9 vs. -0.4+2.6 kcal/kgLBM/d). There was a trend toward a significant difference between the groups (p = .07) for REE relative to body weight (-1.4+1.9 vs. -0.3+1.5 kcal/kg/d). When the groups were combined, there was a correlation between change in REE and change in body weight was r=0.41 (p<.05), and change in REE and change in lean body mass was r=0.44 (p<.01). CONCLUSIONS: Results indicate that absolute and relative REE are significantly reduced in response to weight loss over a 4-week period. The modest correlations between change in REE and both body weight and lean body mass may suggest that additional physiological mechanisms influence REE during the acute phase of weight loss