The effects of weight loss approaches on bone mineral density in adults: a systematic review and meta-analysis of randomized controlled trials

The Summary We assessed the impact of weight loss strategies including calorie restriction and exercise training on BMD in adults using a systematic review of randomized controlled trials. Weight reduction results in reduced BMD at the hip, but has less effect on the spine. Both calorie restriction and a combination of calorie restriction and exercise result in a decrease in hip bone density, whereas weight loss response to exercise training without dietary restriction leads to increased hip BMD. Introduction Findings are not consistent on the effect of weight loss on bone mineral density (BMD). We conducted a systematic review on the randomized controlled trials to assess the effect of weight loss strategies, including calorie restriction and exercise programs on BMD in adults. Methods A structured and comprehensive search of MEDLINE and EMBASE databases was undertaken up to March 2016. Study-specific mean differences (MD) were pooled using a random-effects model. Subgroup analysis and meta-regression were used to find possible sources of between-study heterogeneity. Results Thirty-two randomized controlled trials met predetermined inclusion criteria. The meta-analysis revealed no significant difference on total BMD (MD 0.007, 95 % CI -0.020-0.034, p=0.608). In contrast, the pooled data of studies showed a significant effect of weight loss on hip BMD (MD -0.008, 95 % CI -0.09 to -0.006 g/cm(2), p<0.001) and also lumbar spine BMD (MD -0.018 g/cm(2), 95 % CI -0.019 to -0.017, p<0.001). BMD in the hip site decreased after more than 4 months, especially in those who were obese. Moreover, calorie restriction interventions longer than 13 months showed a significant decreased in lumbar spine BMD. Conclusion Weight loss led to significant decreases at the hip and lumbar spine BMD but not at the total. Weight loss response following calorie restriction resulted in a decrease in hip and lumbar spine bone density especially more than 1 year; whereas an exercise-induced weight loss did not.