Regional, but not total, body composition changes in overweight and obese adults consuming a higher protein, energy-restricted diet are sex specific

Abstract

Secondary analyses of data from 2 studies were used to assess the effects of protein intake and sex on diet-induced changes in body composition. The primary hypothesis was that the changes of body composition via energy restriction (ie, lean body mass [LBM], fat mass [FM], and bone) would be sex and diet specific. For 12 weeks, 43 male (study 1) and 45 female (study 2) overweight and obese adults consumed an energy-deficit diet (750 kcal/d less than energy needs) containing either 0.8 (normal protein [NP], 21 men and 23 women) or 1.4 g protein∙kg(-1)∙d(-1) (high protein [HP], 22 men and 22 women). Body composition measurements were performed at preintervention and postintervention. Over time, all research participants lost weight, LBM, and FM. Independent of protein intake, the men lost more LBM in the trunk (-0.9 vs -0.5 kg) and less in the legs (-1.5 vs -1.1 kg) compared with the women (P < .05). Independent of sex, the HP group lost less LBM in the trunk and legs than the NP group. These sex and protein intake responses resulted in the NP men losing the most LBM in the legs and the NP women losing the most LBM in the trunk. Over time, men lost more FM (-5.0 vs -3.9 kg) from the trunk and less from legs (-1.7 vs -2.1 kg) than women (P < .05), which resulted in a greater decrease of the android-to-gynoid fat ratio for the men. Protein intake did not influence these sex-specific responses or have any independent effects on changes in FM. In addition, protein intake did not influence bone mineral density responses over time; bone mineral density was reduced in women, but not in men. These findings indicate that higher protein intake during weight loss promotes the retention of LBM in both the trunk and legs despite the sex-specific changes in these body regions.

Keywords: BMD; BMI; BUN; Body composition; Bone mineral density; DXA; Dietary protein; Energy restriction; FM; HP; LBM; NP; Weight loss; blood urea nitrogen; body mass index; bone mineral density; dual-energy x-ray absorptiometry; fat mass; high-protein diet; lean body mass; normal-protein diet.

Figure 1

Changes of blood urea nitrogen (BUN) from baseline to post intervention in the normal-protein (NP) and higher-protein (HP) groups. Values are means and error bars.

Figure 2

Changes in body weight, fat mass and lean body mass after a 12-week peiiod of energy restriction (750 kcal/day energy deficit) in men (n=43) and women (n=45) in the normal-protein (NP) and higher-protein (HP) groups. Values are means and error bars.

Figure 3. Regional lean mass losses

Changes in lean mass in the trunk and legs after a 12-week period of energy restriction (750 kcal/day energy deficit) in overweight and obese men (n=43) and women (n=45). There were protein-by-time (P < 0.001) and gender-by-time (P < 0.05) interactions. The main effects of protein and gender were additive. NP: normal-protein diet: HP: higher-protein diet. Values are means and error bars.

Figure 4. Regional fat mass losses

Changes in fat mass in the trunk and legs after a 12-week period of energy restriction (750 kcal/day energy deficit) in overweight and obese men (n=43) and women (n-45). There was an effect of gender-by-time (P < 0.05) in both the trunk and legs, but no effect of dietary protein groups. Values are means and error bars.