Effects of calcium and resistance exercise on body composition in overweight premenopausal women

Abstract

Objective: To examine the combined treatment effect of a mild energy restriction, high dairy calcium intake, and resistance exercise on promoting favorable body composition changes in overweight women with a low dairy intake. Combined treatment strategies may produce synergistic effects on increasing fat loss and preserving bone in a population at risk for obesity and osteoporosis. Methods: Overweight, sedentary women consuming a diet low in dairy calcium (≤1 serving of dairy per day) were randomized either (1) to maintain a low-calcium diet (LOW; ≤ 500 mg; n = 15) or (2) to increase dairy calcium (HIGH; ≥1200 mg; n = 14) for 16 weeks. Both groups began resistance training 3 days per week and received dietary counseling to reduce energy intake by 250 kcal per day. Body composition was measured at the beginning and at the end of the study with dual energy x-ray absorptiometry. Two 24-hour dietary recalls were measured at baseline, midpoint, and end of study with Nutrition Data System for Research software. Results: Participants were 36.8 ± 4.8 years of age, with an average body mass index of 29.1 ± 2.1 kg/m2. Fat mass decreased significantly over time (LOW = 3.8 ± 4.1 kg and HIGH = 1.8 ± 2.1 kg) but was not significantly different by group. Mean energy reduction from baseline was 382 kcal (LOW) and 214 kcal (HIGH; p = 0.14). When change in energy intake was included as a covariate, there was still no significant difference in fat loss between groups. Change in lumbar spine bone mineral density (LOW = −1.5% and HIGH = 0.8%) was significant between groups (p = 0.02). The prescribed mean calcium intake was achieved for each study group (LOW = 454 ± 143 mg and HIGH = 1312 ± 183 mg), with no significant changes in protein intake over time (LOW = 0.9 g/kg and HIGH = 1.0 g/kg, p = 0.08). Conclusion: These results suggest that increasing dairy calcium offers no added benefit in reducing body fat when combined with resistance training and energy restriction. However, increasing dairy calcium improves bone mineral density in premenopausal overweight women. © 2010 American College of Nutrition.