Imposed rate and extent of weight loss in obese men and adaptive changes in resting and total energy expenditure

© 2015 Elsevier Inc. All rights reserved. Objectives. Weight loss (WL) is associated with a decrease in total and resting energy expenditure (EE). We aimed to investigate whether (1) diets with different rate and extent of WL determined different changes in total and resting EE and if (2) they influenced the level of adaptive thermogenesis, defined as the decline in total or resting EE not accounted by changes in body composition. Methods. Three groups of six, obesemen participated in a total fast for 6 days to achieve a 5% WLand a very lowcalorie (VLCD, 2.5 MJ/day) for 3 weeks or a low calorie (LCD, 5.2 MJ/day) diet for 6 weeks to achieve a 10% WL. A four-component modelwas used to measure body composition. Indirect calorimetry was used to measure resting EE. Total EE was measured by doubly labelled water (VLCD, LCD) and 24-hour whole-body calorimetry (fasting). Results. VLCD and LCD showed a similar degree ofmetabolic adaptation for total EE (VLCD = - 6.2%; LCD = -6.8%). Metabolic adaptation for resting EE was greater in the LCD (-0.4 MJ/day, - 5.3%) compared to the VLCD (-0.1 MJ/day, -1.4%) group. Resting EE did not decrease after shortterm fasting and no evidence of adaptive thermogenesis (+0.4 MJ/day) was found after 5%WL. The rate ofWL was inversely associated with changes in resting EE (n = 30, r = 0.-42, p = 0.01). Conclusions. The rate of WL did not appear to influence the decline in total EE in obese men after 10% WL. Approximately 6% of this decline in total EE was explained by mechanisms of adaptive thermogenesis