Effects of Calcium Supplementation on Body Weight and Adiposity in Overweight and Obese Adults

Randomized, placebo-controlled, parallel-group trial conducted at a single research center in the Washington, DC, metropolitan area. Overweight or obese adults were enrolled, with most participants being women; the calcium group had 170 randomized participants and 168 analyzed.

Calcium carbonate providing 1500 mg/day elemental calcium was given orally in 2 divided doses with meals for 2 years, compared with placebo. The regimen evaluated calcium supplementation alone; vitamin D was provided only to participants found to be deficient as needed, not as the primary intervention.

Two years of calcium supplementation did not meaningfully reduce weight gain or fat gain versus placebo. End-of-study weight change was 0.54 kg in the calcium group and 0.52 kg in the placebo group, with a between-group difference of 0.02 kg (P = 0.98). Fat mass change was 0.40 kg versus 0.01 kg, respectively, with a difference of 0.39 kg (P = 0.55), and BMI change was 0.18 kg/m2 versus -0.14 kg/m2 (P = 0.39). The authors concluded that calcium supplementation is unlikely to have clinically significant preventive efficacy for weight gain in overweight or obese adults.

Single-center enrollment and a sample composed mostly of women limit generalizability. The trial duration was long, but the effect estimates were small and nonsignificant, and any benefit on body weight or adiposity was not supported. Some participants required vitamin D treatment for deficiency, which could add minor heterogeneity to the trial context.