I hear this sentence constantly, usually from someone who has dieted seriously for twenty years and is exhausted by it: I think I broke my metabolism. There is real physiology behind that feeling. But "broken" is the wrong word, and it leads people toward exactly the strategies that made things harder.
What Repeated Dieting Actually Does
Each aggressive restriction cycle tends to cost some lean mass, and lean mass is metabolically expensive tissue. Regain, in most people, returns proportionally more fat than muscle. Repeat that several times and you can arrive at the same weight you started with while carrying less muscle and burning less at rest. Nothing broke. The composition changed.
Adaptation Is Real, and Usually Overstated
Beyond the tissue change, the body does reduce energy expenditure somewhat during and after weight loss — more than body size alone predicts. This is measurable and worth respecting. It is also a nudge, not a wall, and it is not permanent damage.
What's Often Actually Going On
- Insulin resistanceFrequently present for years before blood sugar looks abnormal. Markers like HOMA-IR and the triglyceride-to-HDL ratio can reveal it early.
- Underactive thyroidSometimes hiding behind lab values called normal.
- Sex hormone shiftsPerimenopause, menopause and declining testosterone all change body composition.
- Chronic cortisol elevationStress and poor sleep push fat storage toward the abdomen.
- Lost muscleOften the largest single contributor, and the most correctable.
Why the Answer Isn't Eating Even Less
The instinct after a stall is to cut harder. That usually accelerates muscle loss and deepens the adaptation. Building muscle back, eating enough protein, correcting whatever hormonal or metabolic issue is present — that is slower and far less satisfying as advice, and it is what actually works.
This is the reasoning behind Dr. Allen's line in Dr. Allen's book, Why Do I Feel Like This?: I don't recommend diets. Not because effort doesn't matter, but because restriction alone doesn't address the machinery.
Test, Don't Assume
Take the 3-minute quiz or book a consultation for a metabolic workup, and read more about medical weight management.