Effect of Caloric Restriction and Protein Intake on Insulin-like growth factor and Insulin-like growth factor binding protein-3

Previous studies have shown that dietary protein is important for bone health. In addition insulin like growth factor and IGF-binding protein-3 are essential for bone growth and maintenance. Weight loss due to normal caloric restriction can result in a decrease in IGF-1/IGF-binding protein which can have an adverse effect on bone health. The aim of this study was to determine whether IGF-1 and binding protein-3 is associated with lean body mass, bone mass and turnover in overweight and obese postmenopausal women and whether it is altered by the level of dietary protein intake during caloric restriction. It is hypothesized that a high protein diet (HP) compared to a normal protein (NP) diet will prevent a decline in serum IGF-1/binding proteins, normally associated with caloric restriction. In this year- long study postmenopausal women were recruited for weight loss and instructed to follow a reduced calorie, well balanced diet. Participants were placed randomly on either a low-calorie NP or HP diet and consumed the recommended level of calcium and vitamin D. In this analysis, we measured serum IGF-1, IGFBP-3 and body composition (fat, muscle mass, and bone mineral density and content) using dual energy x-ray absorptiometry. Recent research indicates that an increased body mass index is related to greater risk of ankle fracture. A large population of overweight, postmenopausal women would benefit from this study because protein would compensate for weight loss related-reduction in bone mass and would diminish the risk of ankle fracture occurrence.