Weight loss and bone mineral density in obese adults: a longitudinal analysis of the influence of very low energy diets.

Background: The long-term effect of weight reduction on skeletal health is not well understood. The purpose of this study was to examine the impact of an intensive medical weight loss intervention using very low energy diet (VLED) (~ 800 cal/day) that result in significant changes in body weight, on total body bone mineral density (BMD) over 2 years.

Methods: We examined the impact of VLED-induced weight loss on BMD and FFM (Fat-free Mass) after 3-6 months and again while in weight maintenance at 2 years in 49 subjects. The effects of absolute and relative rate of weight reduction assessed by change in weight in kilograms were assessed using general linear modeling, with baseline BMD (or FFM) as a covariate, and age, sex and changes in body weight as primary model predictors.

Results: At the end of 2 years, the average weight loss was greater for men (weight: 23.51 ± 12.5 kg) than women (weight: 16.8 ± 19.2 kg) and BMD loss was greater among women (0.03 ± 0.04 g/cm2 vs 0.01 ± 0.04 g/cm2 ) (all p  < 0.05). After adjusting for baseline BMD, age, and sex, there was a small but significant association between total weight loss and 2-year BMD (β = - 0.001 g/cm2 ; p  = 0.01). Similarly, there was a significant independent association between total weight loss and 2-year FFM (β = - 116.5 g; p  < 0.01).

Conclusions: Despite significant weight loss with VLED, there was only a small loss is BMD.