Weight Gain in a Marathon Runner and Triathlete

A 51-year-old female marathon runner and triathlete experienced a 15-pound weight gain despite rigorous training and a low-calorie diet of 1000–1200 calories per day. She showed no signs of thyroid disease or diabetes, but her resting metabolic rate was 28% below the predicted level. The final diagnosis was over-training and under-eating. Treatment involved gradually increasing her caloric intake to 1500 calories per day, adjusting macronutrient distribution, incorporating resistance training, and taking supplements. After 6 weeks, her resting metabolism increased by 35%, and she lost 5 pounds of body fat, reducing her body fat percentage from 37% to 34%.