Proceedings of The Physiological Society

Physiology 2012 (Edinburgh) (2012) Proc Physiol Soc 27, PC147

Poster Communications

Body composition and resting metabolic rate changes in weight loss programs

J. Butragueño Revenga1, M. Rojo-Tirado1, P. Benito1, R. Cupeiro1, A. Peinado1, P. Study group1

1. Technical University of Madrid, Madrid, Spain.

Physical activity in conjunction with moderate dietary energy restriction has been promoted as an important component of a successful weight-loss regimen (1-4). It has been shown in previous studies that the decrease of fat mass (FM) with low-energy diets is accompanied by a reduction of the fat-free mass (FFM) and the resting metabolic rate (RMR), while physical activity contributes to preserve the FFM, and therefore, the RMR (1, 5). Thus, the aim of this study was to investigate the effect of four different weight loss programs on the FM, the FFM and the RMR, comparing men and women. One hundred eighty overweight and obese people (Body Mass Index: 25-34.9 kg/m2), aged from 18 to 50 years, participated in the study (84 males, 96 females) during 6 months. Four types of treatments were randomly assigned: strength training (S, n=43), endurance training (E, n=51), combined S and E training (SE, n=46), and physical recommendations (C, n=40). All participants followed a 25-30% calorie restriction diet. Body composition and RMR were assessed by dual-energy X-ray absorptiometry (DXA) (Lunar ProdigyTM, General Electric, USA) and by indirect calorimetry (Jaeger Oxycon Pro Gas Analyser, Erich Jaeger, Viasys Healthcare, Germany), respectively. A MANOVA test was used to determine differences among types of treatment and sexes in FM, FFM, and RMR changes. Probability level for statistical significance was set at α=0.05. FM was significantly reduced in all groups (S:-6.69±3.77 kg; E:-6.38±2.94 kg; SE: -7.81±3.31 kg and C:-6.25±4.17 kg) and in women and men (-6.08±3.38 vs. -7.59±3.62 kg, respectively), being the decrease for men significantly higher than the one reported for women. However, no differences were found among the different treatments performed (p>0.05). FFM was maintained in all exercise groups (S, E, and SE), while C group reduced it by-1.15±1.64 kg (p<0.05). Both sexes decreased the FFM (p<0.05). RMR was decreased in S, SE and C groups (from 1814±322 to 1591±415 kcal/day; from 1727±376 to 1629±329 kcal/day; and from 1755±37 to 1631±321 kcal/day, respectively, p<0.05), while in E resulted unaltered (from 1583±351 to 1589±354 kcal/day, p>0.05). Moreover, RMR was significantly reduced in women and men (-102.56±292.06 vs. -112.39±367.55 kcal/day, respectively). In a controlled weight loss intervention the FM lost can be achieved throughout all the four types of treatment analyzed, with or without exercise, in both sexes. However, adding supervised exercise to the calorie restriction contributes to preserve the FFM, after a six-month program. On the other hand, the RMR decreased in all the groups, except the E group. Maybe this can be due to the fact that subjects in the E group had a lower RMR at baseline, and they reach the level of the other groups throughout the 6 month treatment.

Where applicable, experiments conform with Society ethical requirements