“Losing weight permanently damages your metabolism.”
Weight loss can reduce energy use beyond the change expected from a smaller body. A systematic review found variable results, with smaller effects in better-quality studies and often less adaptation after weight stabilizes. A small extreme-weight-loss cohort found adaptation six years later. Persistence is not proof of irreversible damage.
Energy use can fall after weight loss, including more than expected from a smaller body. This response varies and can last for years in some people. The research does not establish that losing weight permanently breaks your metabolism.
Safety note: Do not respond to difficulty maintaining weight with increasingly severe food restriction. Seek help with a manageable plan.
Talk to a healthcare professional if: Discuss concerns about weight maintenance, fatigue or restrictive eating with a clinician or dietitian.
A lower energy requirement can make weight maintenance harder. Calling every slowdown temporary is too simple, but a lasting slowdown is not the same as proven permanent damage.
If maintaining weight is difficult, review your plan and support needs with a clinician or dietitian instead of assuming your metabolism is broken.
Similar claims on Calorie restriction & metabolism impact
Don't fear that eating sensibly less will ruin your metabolism - it won't. Moderate restriction paired with strength training and enough protein is the healthy version; extreme, prolonged restriction is not the goal.