Influence of Protein Intake, Race, and Age on Responses to a Weight-Reduction Intervention in Obese Women

BACKGROUND: Women have higher rates of obesity than men and develop more pronounced functional deficits as a result. Yet, little is known about how obesity reduction impacts their functional status, including whether their responses differ when protein intake is enhanced. OBJECTIVE: To confirm the feasibility of delivery of a higher protein (balanced at each meal) calorie-restricted diet in obese women and determine its efficacy for influencing function and retention of lean mass. METHOD: Obese community dwelling women (n=80; BMI=37.8±5.9 kg/m2), 45 to 78 yrs, 58.8% white) were enrolled in a weight loss (-500 kcal/d) study and randomized to either a Control-Weight Loss (0.8g protein/kg/bw; C-WL) group or a High Protein-Weight Loss (1.2 g protein/kg/bw; 30 g protein 3 times/day; HP-WL) group in a 1:2 allocation. Primary outcomes were function by 6-minute walk test (6MWT) and lean mass by BODPODTM at 0, 4 and 6 mo. RESULTS: Both groups reduced calorie intakes and body weights (P<.001) and feasibility of the HP-WL intervention was confirmed. 6MWT results improved (P<.01) at 4 months in HP-WL and 6 months in both groups (P<.001). Both groups improved function by several other measures while slightly decreasing (P<.01) lean mass (kg) (-1.0 C-WL; -0.6 HP-WL). Weight loss (kg) was greater in white than black women at both 4 (6.0±3.6 versus 3.7±3.4; P<.02) and 6 months (7.2±4.8 versus 4.0±4.7; P<.04) and tended (P<.06) to be positively related to age. CONCLUSIONS: A clinically important functional benefit of obesity reduction was confirmed in both study groups, with no significant group effect. Our findings of racial differences in response to the intervention and a potential influence of participant age lend support for further studies sufficiently powered to explore the interaction of race and age with functional responses to obesity reduction in women.