A new U.S. study shows that weight loss in middle-aged women may lead to osteoporosis. The study also suggests that middle-aged women who lost a moderate amount of weight lost more bone density than men and younger women, regardless of the type of food or calcium content in their diet. The study was published in the Journal of Clinical Endocrinology and Metabolism (JClin Endocrinol Metab). Meryl LeBoff, PhD, of Brigham and Women’s Hospital, and colleagues analyzed data from 424 participants in a large weight-loss study. The participants were 30 to 70 years old, all were overweight or obese at the beginning of the study, and 60% were women who were randomly assigned to receive four low-calorie diets (two high protein and two moderate protein). Spine and hip bone mineral density was measured at the beginning of the study, 6 months and 2 years after dietary treatment. At the end of the 2-year study, a total of 236 men and women completed the study men and women lost 8% and 6.4% of their initial body weight, respectively. With comparable weight loss, the spine and hip BMD decreased in the menopausal group while the spine BMD increased in the men and the hip BMD remained stable. Only hip BMD decreased in postmenopausal women. Decreased abdominal fat in postmenopausal women is associated with a reduced risk of cardiovascular disease and diabetes, but is also strongly associated with bone loss. Decreased muscle mass also affects osteoporosis because muscle mass has an important role in bone. Compared to women, men experience more fat loss than lean body mass in weight loss. Lean body mass and fat mass loss in postmenopausal women were associated with both spine and hip bone density loss. The researchers said that while weight loss has benefits for most cardiovascular and other health outcomes, bone health is also an important issue that should be considered, especially since weight loss in women may lead to osteoporosis, which in turn leads to a significant increase in fracture risk in women.