To study the influence of excess body weight on vertebral postmenopausal bone loss, 155 healthy early postmenopausal women were divided into 2 groups according to their body mass index (BMI = weight/height2) and prospectively followed over a mean 31-month period. Spinal (L2-L4) bone mineral density was measured by dual photon absorptiometry. The annual rate of vertebral bone loss (percentage) was significantly reduced (-0.54 +/- 1.1% vs. -1.46 +/- 1.6%; P < 0.05) in the overweight group (BMI, > or = 25; n = 40) compared to that in the normal weight group (BMI, < 25; n = 115). At baseline, a significant decrease in the urinary calcium/creatinine ratio was observed in the overweight group, which suggested a decrease in bone turnover. A significant correlation was found between the annual rate of bone loss and the BMI (r = 0.21; P < 0.05), but not the body weight. The positive correlation between vertebral postmenopausal rate of bone loss and BMI was confirmed after adjustment for age and time since menopause. Moreover, plasma dehydroepiandrosterone sulfate levels were higher in the high BMI group than in the normal BMI group (P < 0.05). We conclude that within the first years after menopause, moderate excess body weight significantly reduces vertebral postmenopausal bone loss. This effect is probably related to excess adipose tissue through increased conversion of estrogen from adrenal precursors and/or increased production of adrenal androgens.