The Effect of Severe Weight Loss and Protein Intake on Bone

It is unclear whether the amount of protein in the diet during caloric restriction influences bone density. This information is important for determining optimal nutrient requirements during weight loss. This study will examine usual and higher dietary protein intake during severe weight loss following weight loss surgery on bone turnover, mass and quality in women, with the hypothesis that higher protein intake will reduce bone turnover and loss, and/or prevent the changes in bone quality associated with severe weight loss in women ages 18 to 70 years.

Participants will be randomly assigned to one of 2 groups: A) weight loss with recommended level of protein intake, or B) weight loss with higher protein intake. A dietitian will provide instructions for a reduced calorie, well balanced diet throughout the 12-month study using a nutrition-education behavior- modification program. Participants will have the opportunity to speak with the dietitian about their diet by phone, or on-site twice per month. In addition they will be asked to take a daily vitamin/mineral supplement and, depending on their usual food intake, they may be asked to take a calcium tablet to meet the recommended intake throughout the study period. Bone, mineral, protein and lipid markers, and hormones that influence bones will be measured. These measurements will provide information about body composition (fat, muscle mass, and bone mineral density).