Areal and volumetric bone mineral density and geometry at two levels of protein intake during caloric restriction: a randomized, controlled trial

Abstract

Weight reduction induces bone loss by several factors, and the effect of higher protein (HP) intake during caloric restriction on bone mineral density (BMD) is not known. Previous study designs examining the longer-term effects of HP diets have not controlled for total calcium intake between groups and have not examined the relationship between bone and endocrine changes. In this randomized, controlled study, we examined how BMD (areal and volumetric), turnover markers, and hormones [insulin-like growth factor 1 (IGF-1), IGF-binding protein 3 (IGFBP-3), 25-hydroxyvitamin D, parathyroid hormone (PTH), and estradiol] respond to caloric restriction during a 1-year trial using two levels of protein intake. Forty-seven postmenopausal women (58.0 ± 4.4 years; body mass index of 32.1 ± 4.6 kg/m(2) ) completed the 1-year weight-loss trial and were on a higher (HP, 24%, n = 26) or normal protein (NP, 18%, n = 21) and fat intake (28%) with controlled calcium intake of 1.2 g/d. After 1 year, subjects lost 7.0% ± 4.5% of body weight, and protein intake was 86 and 60 g/d in the HP and NP groups, respectively. HP compared with NP diet attenuated loss of BMD at the ultradistal radius, lumbar spine, and total hip and trabecular volumetric BMD and bone mineral content of the tibia. This is consistent with the higher final values of IGF-1 and IGFBP-3 and lower bone-resorption marker (deoxypyridinoline) in the HP group than in the NP group (p < .05). These data show that a higher dietary protein during weight reduction increases serum IGF-1 and attenuates total and trabecular bone loss at certain sites in postmenopausal women.

Copyright © 2011 American Society for Bone and Mineral Research.

Figures

Fig. 1

Flowchart of study participants.

Fig. 2

The percent change in bone mineral density (BMD) compared with baseline at all sites in the HP and NP groups at 1 year. Comparison of percent change between two groups was done by one-way ANOVA. ap <.05.

Fig. 3

Changes in 25-hydroxyvitamin D [25(OH)D], parathyroid hormone (PTH), estradiol, insulin-like growth factor 1 (IGF-1), and insulin-like growth factor–binding protein 3 (IGFBP-3) during the intervention in the two groups. The influence of diet over time on these hormones was analyzed by two-factor repeated-measures ANOVA (diet × time =D × T). Values with different superscript letters are significantly different. Diamond and dotted line represents HP (n =26); square and solid lines represent NP (n =21).