A randomized trial of exercise and diet on body composition in survivors of breast cancer with overweight or obesity

Purpose: Obesity increases the risk of cancer recurrence and death in survivors of breast cancer. This study tested the hypothesis that exercise alone, diet alone, and the combination of exercise plus diet reduce body weight and improve body composition in survivors of breast cancer. Methods: In this 2 × 2 factorial trial, 351 survivors of breast cancer with overweight or obesity were randomized to one of four treatment groups for 52 weeks: control, exercise alone, diet alone, or exercise plus diet. Endpoints included body weight and body composition measured by dual-energy x-ray absorptiometry. Results: After 52 weeks, compared with control, diet alone [− 5.39 kg (95% CI − 7.24, − 3.55);− 6.0% (95% CI − 8.0, − 3.9)] and exercise plus diet [− 6.68 kg (95% CI − 8.46, − 4.90);− 7.4% (95% CI − 9.4, − 5.4)] reduced body weight; exercise alone did not change body weight. Compared with control, diet alone [− 3.59 kg (95% CI − 5.00, − 2.17)] and exercise plus diet [− 4.28 kg (95% CI − 5.71, − 2.84)] reduced fat mass; exercise alone did not change fat mass. Compared with control, diet alone [− 0.82 kg (95% CI − 1.50, − 0.15)] and exercise plus diet [− 1.24 kg (95% CI − 1.92, − 0.56)] reduced lean mass; exercise alone did not change lean mass. Compared with control, exercise alone, diet alone, and exercise plus diet did not change bone mineral density. Conclusion: In survivors of breast cancer with overweight or obesity, diet alone or diet plus exercise produced clinically meaningful weight loss at week 52. The majority of weight loss was fat mass.