Energy Intake Response to Short-Term Alterations of Energy Expenditure in Humans

Detailed Summary

One reason people gain weight is eating more calories from food than what they need for energy over 24 hours. Metabolism is the amount of energy a person uses over 24 hours. Researchers want to study the relationship between changes in metabolism and how much a person eats. Objectives: To see how much food a person eats when the body's temperature is cooled. To study how changes in metabolism may alter the amount of food a person eats. Eligibility: Healthy people ages 18-55. Design: Participants will stay at NIH for 20 days. During the first 4 days, participants will have: * Medical exam * Electrocardiogram * Blood and urine tests. One blood test includes drinking a sugar solution. * DXA body composition scan * Questions about foods they like, physical activity, and personal behavior * Exercise test on a stationary bicycle Participants will spend 24-hour periods in a metabolic chamber. The chamber will be at normal room temperature or cooler. Some times, participants will eat a diet that matches their daily needs (fixed or eucaloric). Other times, they can eat as much as they wish from a vending machine (ad libitum). Participants will have blood and urine collected. Participants will swallow an ingestible wireless sensor and wear a small data recorder device. On the second to last day, participants will stay in the metabolic chamber but only consume water and non-caffeinated sugar-free beverages. Participants will come back for 1-day visits at six months and one year from the first admission. They will have blood and urine tests, and a DXA scan. They will answer questions on physical activity and food habits.

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