The hunger that doesn't fade: appetite hormones stay changed a year after weight loss

In 2011, a team in Melbourne led by Priya Sumithran set out to answer a deceptively simple question: once you have lost weight, do the hormones that govern hunger settle back to normal? Fifty overweight or obese adults without diabetes followed a very-low-energy diet for ten weeks, losing an average of 13.5 kg. The researchers then measured a panel of appetite-regulating hormones — and subjective hunger — at the start, at the end of the diet, and again at week 62, roughly a year after the weight came off.

The findings were sobering. Ghrelin, the hormone that drives hunger, was significantly raised at ten weeks and was still elevated a year later. The satiety hormones moved the other way and stayed there: leptin, peptide YY (PYY) and cholecystokinin (CCK) were all suppressed at week 62 relative to baseline. And the people themselves were hungrier — self-reported appetite was significantly higher at one year than before they had ever dieted, even though they had regained only part of the lost weight.

In other words, the hormonal environment of someone who has dieted down does not resemble that of someone who has always been that size. It resembles the environment of a body that is being actively defended against further loss — a body, in effect, asking to be fed back up. The adaptations had not normalised within a year. They persisted.

This study reframed weight regain as a physiological consequence rather than a failure of resolve. If hunger is amplified and satiety blunted twelve months on — measurably, hormonally — then the person maintaining weight loss is not simply choosing badly; they are working against a coordinated biological signal that does not tire and does not relent.

The clinical implication is considerable. It supports treating obesity as a chronic, relapsing condition that needs ongoing management, much as hypertension does, rather than a problem to be solved once with a finite course of dieting. It also helps explain why pharmacotherapy that modulates the appetite system — the GLP-1 receptor agonists chief among them — tends to require continued use to hold its effect: stop the treatment and the underlying defended state, the one Sumithran's data made visible, is still there. The honest message for patients is that regain after dieting is largely biology, not weakness, and that durable maintenance usually needs a durable intervention.