Resting energy expenditure adaptation after short-term caloric restriction in morbidly obese women

Objective:The objective of this study was to describe changes in the resting energy expenditure, substrate oxidation rate, and body composition in morbidly obese women subjected to short-term caloric restriction. Methods:This was a prospective study that included ten obese women with body mass index greater than 40 kg/m2 and aged between 20-50 years. The participants were hospitalized for eight days and received a controlled conventional low-calorie diet, 1200 kcal/day, for seven days. Body weight, body mass index, abdominal circumference, body composition, resting energy expenditure, and substrate oxidation rate were evaluated at the beginning and at the end of the study. Results:A significant reduction in body weight (p=0.005), body mass index (p=0.005), abdominal circumference (p=0.005), fat mass (p=0.005) and fat-free mass (p=0.008) was observed at the end of the study. There was an average reduction in resting energy expenditure of approximately 124 kcal/day (5%). Substrate oxidation rate did not show statistically significant changes. There was a positive correlation only between body weight reduction and fat-free mass reduction (r=0.753; p=0.012). Conclusion:There was an adaptive response of the resting energy expenditure with short-term energy restriction in morbidly obese women with a 5% reduction in resting energy expenditure and a positive correlation between weight loss and the fat-free mass, which indicates the influence of fat-free mass on the decrease in resting energy expenditure. Therefore, short-term caloric restriction in morbidly obese women led to a decrease in resting energy expenditure and fat-free mass, which suggests a rapid adaptation of energy expenditure