Six RCTs (794 participants) were included in the review. Sample sizes ranged from 43 to 340. Methodological quality of the studies was variable. Only two studies reported using adequate randomisation, allocation concealment and sample size calculations; one RCT reported adequate blinding of outcome assessors and use of intention-to-treat analysis. The authors reported that that five of the RCTs were not of good reporting quality.
There was a small but statistically significant reduction in body weight for calcium supplementation in comparison with placebo (MD -0.74kg, 95% CI -1.00 to- 0.48, I2=9%; seven RCTs) and body fat (MD -0.93kg, 95% CI -1.16 to -0.71, I2=44%; seven RCTs). There was no statistically significant differences between calcium supplementation and placebo for BMI (I2=42%; four RCTs).
None of the studies reported data on adverse events. Subgroup analysis revealed a statistically significant decrease in body weight in premenopausal women that favoured calcium over placebo (three RCTs), but no decrease in body weight in postmenopausal women (three RCTs).
A funnel plot showed some evidence of publication bias; sensitivity analyses did not significantly alter the main findings.