Metabolic adaptation is the body’s response to chronic calorie restriction: lowered metabolic rate, decreased energy expenditure, increased hunger. Research by Zauner found resting energy expenditure actually increases during short-term fasting—the opposite of chronic restriction. Fothergill’s study of Biggest Loser contestants showed metabolic suppression persisting 6 years after weight loss. The key difference is hormonal: restriction signals scarcity; fasting signals temporary fuel switching.
This companion covers the metabolic adaptation problem, the hormonal environments, why fasting differs, and practical implications. (4 min read)