Résumé
Although body mass is known to be related to bone mass, defined as bone mineral density (BMD) and bone mineral content (BMC), little is known about the effects of body mass reduction programs on bone mass. This study assessed bone mass changes in response to four body mass reduction programs that utilized diet and/or exercise. Ninety-four obese or overweight women (age 49.3±7.1 years, body mass 68.5±7.7 kg) were randomly assigned 4 groups (2 intervention forms × 2 trials) : diet in trial 1 (D<SUB>1</SUB>, n=27), diet plus exercise in trial 1 (DE<SUB>1</SUB>, n=28), diet in trial 2 (D<SUB>2</SUB>, n=21), and diet plus exercise in trial 2 (DE<SUB>2</SUB>, n=18) . Body mass, body mass index (BMI), absolute and relative (%fat) fat mass, lean mass, BMC, and BMD were measured by dual energy X-ray absorptiometry before and after the 3-month intervention program. Body mass loss was similar in DI (-9.7%) and D<SUB>2</SUB> (-11.6%), and in DE<SUB>1</SUB> (-13.8%) and DE<SUB>2</SUB> (-12.2%) . However, BMC loss was different (<I>P</I><0.05) between trial 1 and trial 2 for each intervention form (D<SUB>1</SUB>: -3.2% vs D<SUB>2</SUB> ; -0.9%, DE<SUB>1</SUB>: -4.5% vs DE<SUB>2</SUB>: -0.8%) . With this in mind, multiple regression analyses were applied, with either change in BMC or BMD as the dependent variable, and other physical characteristics measured before and after the intervention program as independent variables. Results indicated that multiple correlation coefficients were statistically significant (R=0.61 with BMC, R=0.49 with BMD) . BMI after the intervention program and change in body mass were identified as the significant contributors to the change in BMC, while change in %fat and age were identified as the significant contributors to the change in BMD. These results suggest that, during body mass reduction, (1) physical characteristics are the significant contributors to changes in BMC and BMD and (2) exercise may not prevent the loss of bone mass.