Why the body’s appetite hormones fight to restore lost weight.
What the evidence says
- After diet-induced weight loss, appetite-regulating hormones change to encourage weight regain[1]
- One year after weight reduction, these hormonal changes persist — they do not revert to pre-weight-loss levels[1]
- Leptin drops after weight loss, reducing satiety signals — you feel less satisfied[1]
- Ghrelin (hunger hormone) rises after weight loss, increasing hunger drive[1]
- Subjective appetite ratings remain elevated one year post-weight-loss[1]
- The hormonal profile is consistent with biological pressure to regain, and was still present at one year — the longest interval this study measured. The study does not establish that the persistence caused regain: it is single-arm, and no participant’s regain was tested against their own hormone profile[1]
- Leptin replacement during maintenance of reduced weight reversed two-thirds of the fall in TEE and activity energy expenditure, while increasing skeletal-muscle work efficiency. The effect is specific to that state — the same source records that leptin itself had no effect on energy expenditure in leptin-deficient or overweight patients, which is what makes it evidence about post-weight-loss suppression rather than about leptin raising expenditure generally[2]
- For each kilogram lost, it has been estimated that appetite increases by about 100 kcal/day above pre-weight-loss baseline while calorie expenditure decreases by about 20-30 kcal/day[3]
- Appetite changes likely play a more important role than slowing metabolism in explaining the weight-loss plateau, because the feedback circuit controlling long-term calorie intake has greater overall strength than the one controlling expenditure[3]
- In a mathematical-model illustration of a 90 kg woman reaching a plateau within the first year, calorie expenditure dropped by less than 200 kcal/day while appetite rose by 400-600 kcal/day and energy intake rose by 600-700 kcal/day[3]
- In that model, the exponential rise in calorie intake from its initially reduced value — not the decrease in expenditure — is the primary factor halting weight loss within the first year[3]
- Appetite regulation occurs in brain regions below conscious awareness, potentially causing portion sizes to drift upward without detection[3]