Bone mineral density response to caloric restriction-induced weight loss or exercise-induced weight loss - A randomized controlled trial

Background: Bone loss often accompanies weight loss induced by caloric restriction (CR), but whether bone loss accompanies similar weight loss induced by exercise ( EX) is unknown. We tested the hypothesis that EX-induced weight loss is associated with less bone loss compared with CR-induced weight loss. Methods: Forty-eight adults ( 30 women; 18 men; mean +/- SD age, 57 +/- 3 years; and mean +/- SD body mass index, 27 +/- 2 kg/m(2)) were randomized to 1 of 3 groups for 1 year: CR group (n=19), regular EX group (n=19), or a healthy lifestyle (HL) control group (n=10). Primary outcome measure was change in hip and spine bone mineral density (BMD). Secondary outcomes were bone markers and hormones. Results: Body weight decreased similarly in the CR and EX groups (10.7% +/- 6.3% [-8.2 +/- 4.8 kg] vs 8.4% +/- 6.3% [-6.7 +/- 5.6 kg]; P=.21), whereas weight did not change in the HL group (-1.2% +/- 2.5% [-0.9 +/- 2.0 kg]). Compared with the HL group, the CR group had decreases in BMD at the total hip (-2.2% +/- 3.1% vs 1.2% +/- 2.1%; P=.02) and intertrochanter (-2.1% +/- 3.4% vs 1.7 +/- 2.8%; P=.03). The CR group had a decrease in spine BMD (-2.2% +/- 3.3%; P=.009). Despite weight loss, the EX group did not demonstrate a decrease in BMD at any site. Body weight changes correlated with BMD changes in the CR (R=0.61; P=.007) but not in the EX group. Bone turnover increased in both CR and EX groups. Conclusions: CR-induced weight loss, but not EX-induced weight loss, is associated with reductions in BMD at clinically important sites of fracture. These data suggest that EX should be an important component of a weight loss program to offset adverse effects of CR on bone.