Obese adults who lose weight may experience a small decrease in bone density of the hip but the change is small in comparison to the metabolic benefits gained, researchers say.

The meta-analysis of 41 trials found diet-induced weight loss was associated with significant decreases of 0.010 to 0.015 g/cm2 in total hip BMD for diet interventions lasting up to two-years.

The decrease in total hip BMD occurred alongside statistically significant increases in serum concentrations of osteocalcin, CTX, and NTX, suggesting that weight-loss diets increase bone turnover, said the authors from the Boden Institute of Obesity, Nutrition, Exercise & Eating Disorders, at Sydney University.

No effect was seen for lumbar spine or whole-body BMD but total body BMD decreased after six months.

“It is not clear whether the significant reduction in total hip BMD represents a maladaptive change, or whether it simply represents normalization of BMD relative to reduced body mass after diet-induced weight loss,” they wrote in the Journal of Bone Mineral Research. 

Nevertheless the change is small in comparison to the benefits for metabolic health, they said.

“Clinicians should continue to recommend weight loss for the treatment of overweight and obesity, with support for weight maintenance after weight loss,” they concluded.