Effect of protein supplementation on hip bone mineral density, cortical thickness, and bone strength in older adult participants during a caloric restriction and aerobic exercise weight loss intervention: a randomized controlled trial.

Abstract

Weight loss in older age can cause bone loss. In older adults with overweight/obesity in a weight loss trial, 6-month hip bone strength increased with higher protein intake versus controls consuming the Recommended Dietary Allowance. However, greater weight loss was associated with greater 18-month hip bone mineral density loss. Weight loss (WL) to treat obesity in older age can exacerbate bone loss. This trial assessed the effects of higher protein intake on hip bone outcomes in 187 older adults with overweight/obesity participating in 6 months of active WL (caloric restriction + aerobic exercise) followed by a 12-month maintenance phase. Participants were randomized to either the Recommended Dietary Allowance for protein intake of 0.8 g protein/kg body weight/day (RecProt) or higher protein intake of 1.2 g protein/kg/day for the 6-month WL period only (6-mo HiProt) or the full 18-month period (18-mo HiProt). CT scans at baseline, 6 months, and 18 months were analyzed for hip volumetric bone mineral density (vBMD) and cortical thickness; bone strength was assessed via finite element modeling of a sideways fall. Areal (a)BMD was measured with hip dual-energy X-ray absorptiometry. Analyses examined 6-month and 18-month bone changes using analysis of covariance, and Spearman's correlations of WL vs. bone changes. Greater WL was associated with greater gains in hip bone strength (p = 0.007) at 6 months, but greater trabecular vBMD loss at 18 months (p = 0.011) and aBMD loss at 6 and 18 months (p < 0.001). Hip bone strength increased 3.8 ± 1.7% over 6 months in the 18-mo HiProt group vs. 0.5 ± 1.6% in the RecProt group (p = 0.02) despite similar 6-month WL across groups (-8.0 ± 5.0%); however, there were no differences between the other groups. Eighteen-month group differences were non-significant. Higher protein intake had a beneficial effect on hip bone strength in older adults with overweight/obesity undergoing a WL intervention over the short-term.