Submitted to: European Journal of Clinical Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/18/2003
Publication Date: 7/1/2004
Citation: Van Loan, M.D., Keim, N.L., Stern, J., Bacon, L. 2004. Low bone mass in pre-menopausal chronic dieting obese women. European Journal of Clinical Nutrition. European Journal of Clinical Nutrition. 58:966-971. Interpretive Summary: Osteoporosis is a disease that affects 25 million Americans, 80% of whom are women. Action can be taken to help reduce the amount of bone loss during menopause and thus reduce the risk of osteoporosis. Obese women are generally thought to be at low risk for osteoporosis because of the increased weight on the skeleton. However, other research has suggested that dieting practices can have a negative effect of bone health. Therefore, if overweight and obese individuals participate in numerous episodes of dieting to lose weight they may be inadvertently increasing their risk for low bone mass and/or osteoporosis. To study this issue 78 premenopausal healthy obese women participated in a "Healthy Living Project". Women had a history of chronic dieting. Low bone mass was observed in 31% of the women based on bone scans of the spine and femur. No biological cause could be found to explain the low bone mass except the history of chronic dieting. Significant negative relationships were observed between the number of times women participated in weight lose diets, dieting restraint, and bone mass. These results suggest that repeated dieting may led to low bone mass in otherwise healthy obese women.
Technical Abstract: Obese pre-menopausal women are thought to be at low risk for osteoporosis due to increased body weight and estrogen on weight-bearing bone. However, research involving eating behaviors has identified an association between high levels of restrained eating (conscious limitation of food intake) and reduced bone mass. In order to examine the effect of restrained eating on obese women, we examined bone mineral density (BMD) and content (BMC) of the spine and femur in obese women who were restrained eaters, with emphasis on the relationship between bone mineral content (BMC) and determinants of bone mass, and current eating behaviors, dietary intake, physical activity, and indices of calcium regulation, bone metabolism, stress and inflammation. Seventy-eight obese, Caucasian, female, restrained eaters, ages 30-45 years, were studied. Height, weight, bone turnover markers, serum parathyroid hormone (PTH), cortisol, c- reactive protein (CRP), dietary intake, eating behaviors, physical activity, and BMD and BMC were measured. Thirty-one percent of women had osteopenia or osteoporosis (osteo). In "osteo" women, 87.5% had osteo based on lumbar spine, whereas only 12.5% had osteo based on femur. No significant differences were observed between "osteo" women and "non-osteo" women for current eating behaviors, dietary intake, physical activity habits, bone turnover, calcium regulation, stress or inflammation. A significant positive correlation between BMC and energy expenditure (r=0.256), and a significant negative correlation between BMC and number of times on a weight loss diet (r= -0.250) and cognitive restraint (r= -0.239) were observed. Obese restrained eaters are at risk for low bone mass. Prior dieting may be responsible. Measurement at the lumbar spine is a more sensitive indicator of low bone mass than measurement at the femur in this population.