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 AE 4.4 years; body mass index of 32.1 AE 4.6 kg/ m 2 ) completed the 1-year weight-loss trial and were on a higher (HP, 24%, n ¼ 26) or normal protein (NP, 18%, n ¼ 21) and fat intake (28%) with controlled calcium intake of 1.2 g/d. After 1 year, subjects lost 7.0% AE 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. ß

The dietary protein, IGF-I, skeletal health axis

“…Increasing the protein consumption from 0.8 g/kg bw/day [Recommended Dietary Allowance (RDA)] to 2.4 g/kg bw/day did not negatively affect Ca homeostasis and bone turnover [98]. This observation is in keeping with a long-term study in postmenopausal women with elevated BMI showing that a higher protein diet during weight reduction increases circulating IGF-I and attenuates total and trabecular bone loss at several skeletal sites including ultradistal radius, lumbar spine, and total hip [102]. See section on "Dietary protein-IGF-I axis on bone mineral economy and metabolism" against the hypothesis of a causal relationship between protein intake and systemic acidosis leading to increased bone resorption and eventually age-related osteoporosis.…”

Does Diet-Induced Weight Loss Lead to Bone Loss in Overweight or Obese Adults? A Systematic Review and Meta-Analysis of Clinical Trials

“…The following data was extracted from each study, as summarized in Supporting Table 1: the number of participants in the study (sample size), the sex, menopausal status, age, and baseline BMI of participants (calculated from height and weight where BMI was not reported), duration and details of the dietary weight-loss intervention, time points at which outcomes were collected and used in this review, baseline weight, weight change from baseline at the end of the intervention, and results from one or more of the following parameters: BMD of the total hip, lumbar spine (L 1 -L 4 or L 2 -L 4 ) or of the total body, or circulating or urinary P1NP, osteocalcin, CTX, and NTX concentrations. Some studies included more than one intervention that matched our inclusion criteria (20,22,26,28,29,32,37,42,43,(68)(69)(70) In these instances, data from the different dietary weight-loss interventions were not pooled but were instead treated as independent interventions. For studies that reported both sexes independently, (20)(21)(22)24,29,42,44,(71)(72)(73)(74)(75) data from both sexes were pooled before inclusion in our analysis.…”

“…Corresponding authors were contacted if any required data was not available from the publication or was published in a format different from that required for this meta-analysis. (20,(22)(23)(24)(25)28,(35)(36)(37)39,(42)(43)(44)(45)(46)(47)(69)(70)(71)73,74) For authors from whom we did not receive a response, (24,49,75) data for their publications were analyzed qualitatively rather than quantitatively.…”

“…Of the studies that have investigated changes in bone mass in response to diet-induced weight loss in overweight or obese adults, the results have been highly variable, with increases, (20)(21)(22)(23)(24) decreases, (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40) and no change (22,24,26,30,33,(41)(42)(43)(44)(45)(46)(47)(48)(49) in bone mass being reported. Thus, attempting to draw sound conclusions from these mixed results is extremely difficult.…”

Effects of obesity treatments on bone mineral density, bone turnover and fracture risk in adults with overweight or obesity

“…Similarly, in a randomized controlled trial in overweight pre-menopausal women, both adequate as well as high calcium intakes were shown to attenuate BMD loss during weight loss [90]. In addition, randomized controlled trials have found that higher protein diets (~86 g/day or 24% of energy intake) confer protection against significant bone loss and may decrease bone turnover during diet-induced weight loss [12,37,93,108]. The benefits of vitamin D supplementation to preserve hip BMD during dietary restriction-induced weight loss have recently been called into question, with the observation that it did not attenuate hip BMD loss in a randomized placebo-controlled trial involving 218 post-menopausal women with vitamin D insufficiency [109].…”