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 was diagnosed with over-training and under-eating, as her resting metabolic rate was 28% below the predicted level. The treatment involved gradually increasing her caloric intake to 1500 calories per day, adjusting macronutrient composition, consuming multiple small meals, incorporating resistance training, and taking a daily multivitamin. After 6 weeks, her resting metabolism increased by 35%, and she lost 5 pounds of body fat, reducing her total body fat to 34%.