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 rising rather than falling in short-term fasting — a small study, and the larger one puts the rise at 6% by 36 hours, gone by 72 and absent in men. 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)
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