Differential effects of calorie restriction and involuntary wheel running on body composition and bone structure in diet‐induced obese rats

Abstract

Weight reduction is recommended to reduce obesity-related health disorders. This study investigated the differential effects of weight reduction through caloric restriction and/or physical activity on bone structure and molecular characteristics of bone metabolism in an obese rat model. We tested the hypothesis that caloric restriction is the most effective approach in reducing adiposity, but not improving bone structure in obesity induced by a high-fat diet. Male 6-wk-old Sprague Dawley rats were randomly assigned to six treatments, were fed ad libitum a normal-fat (NF, 10% energy as fat) diet for 6 months or a high-fat (HF, 45% energy as fat) diet for 3 months, and then continue on the HF diet with or without restriction or exercise for an additional 3 months (Figure) . Compared to the HF diet, caloric restriction alone (HF+8CR and HF+16CR) or with exercise (HF+Ex+8CR) decreased fat mass and percent adiposity. Caloric restriction was detrimental to bone microstructure. Compared with the HF group, the HF+8CR group had lower serum tartrate-resistant acid phosphatase (TRAP, a bone resorption marker) and BV/TV at distal femur(p < 0.05) and the HF+16CR had lower serum IGF-1, osteocalcin (bone formation marker), TRAP, BV/TV at both distal femur and 2nd lumbar vertebrae (L2). Exercise combined with caloric restriction (HF+Ex+8CR) decreased serum TRAP and tended to increase BV/TV at distal femur (p = 0.07), compared to the HF group. These data indicate that caloric restriction was more effective at decreasing bodyweight and adiposity than exercise alone, but was detrimental to bone structure. Caloric restriction combined with moderate exercise improved bone mass while decreasing fat mass. Support or Funding InformationThe study was supported by USDA ARS “Food Factors to Prevent Obesity and Related Diseases”, Project Plan. 3062-51000-053-00D