Resting energy expenditure: a stronger marker than body weight for bone mineral density in white women but not men? The Rancho Bernardo study.

OBJECTIVE

To investigate the association between resting energy expenditure (REE) and bone mineral density (BMD) in white adults.

DESIGN

Cross-sectional study.

SETTING

White, middle-class to upper middle-class community-dwelling adults.

PARTICIPANTS

Women (n = 996) and men (n = 686) aged 36 to 97 years.

ASSESSMENT OF RISK FACTORS: REE calculated using the Harris-Benedict equation.

MAIN OUTCOME MEASURES: BMD of the lumbar spine (L1 to L4), total hip, and total body measured using dual energy x-ray absorptiometry.

RESULTS

REE was lower in women than in men (1220 versus 1566 kcal/day, P < 0.0001); women also had lower BMI. After adjusting for lean body mass (LBM), REE was higher in women than men (1407 versus 1296 kcal/kg LBM/d, P < 0.0001). In stepwise multiple linear regression models, REE explained 13% of variance in spine BMD in women and 6% in men, 33% of variance in hip BMD in women and 22% in men, and 32% of variance in total body BMD in women and 22% in men. In women, weight explained 10% less of the hip BMD variance and 6% less of the total body BMD variance than REE. In men, weight explained 4% more of the spine BMD variance and 1% more of the total body BMD variance than REE.

CONCLUSIONS

REE explained more of the BMD variance than weight in women, and the reverse was true in men. These sex differences were largely explained by sex differences in LBM or weight.