"Don't start a diet if you're going to stop it — you'll ruin your metabolism forever." A sentence that has stopped thousands of people from trying. Let's examine it against the evidence.
What did the review find?
A review of current evidence on the physiological effects of weight cycling (Current Obesity Reports, 2024) concluded that the overwhelming majority of evidence finds no adverse effects of weight cycling on body weight, body composition or metabolic rate[1],[2]. In detail:
with body weight gain
in fat mass
in metabolic rate
So why did the myth spread?
Because older studies did not separate weight cycling itself from accompanying factors: pre-existing conditions, ageing, and cumulative exposure to obesity. Once these are properly accounted for, the supposed harms largely disappear[3].
The important message
Intermittent weight reduction — even if not permanently maintained — provides meaningful periods of improved metabolic health and quality of life[3]. Meaning: trying and failing is not harmful, and refusing to try for fear of regain is in fact the worse choice.
But don't misread it
This is not a licence for repeated harsh deprivation cycles. The goal remains sustainable change — the difference is that you now know your previous stumbles did not damage your body, and the door to another attempt is as open as it ever was. (And for maintaining afterwards, see the six habits of successful maintainers.)