We used to say that dieting to lose weight that you just put back on was worse than just staying steady. As with a lot of what we preach in the business of medicine, now we are preaching the opposite.
After weight loss by dieting when you put the weight back on and you’re eating more and gaining weight at least for awhile that can’t be healthy. But there is very little real evidence that this is detrimental. (1)
A study of this question using humans, whether weight cycling is damaging to anything besides your self esteem would be impossible. That’s why a new study report (2) using obese mice, that is making the rounds of the pundits, (2,4) is so important. Using an obesity model in mice they showed that weight cycling – losing weight and then putting it back on – led to longer life than just staying obese.
The life span of a mouse is only about one and a half years but it was still an original and time consuming project to wait for all the mice to die “naturally.” There was a group of obese mice that were calorie restricted for the rest of their lives and those mice lived the longest – 23% longer than the mice allowed to keep eating and stay obese. But there was a group of mice that they restricted and then allowed to eat up back to obese 3 times in their lives and those mice lived 12% longer than the mice left fat. So yo-yo dieting was better than not. Apparently whatever benefit you get from temporarily losing weight beats the damage from eating more and gaining the weight back, at least if you’re an obese mouse.
The authors commented: “To the extent to which these findings represent those that might occur in humans, our results suggest that persons with obesity may benefit from weight loss in terms of longevity, even if the lost weight is regained and the loss-gain cycle is repeated multiple times. If so, perhaps weight loss is not so ill-fated a resolution after all.”
This is in line with the new fad of intermittent fasting that seems to renew your body and lead to a better longer life that we’ve discussed in prior fat science articles.
But that other liability of yo-yo dieting is the discouragement from not getting to stay thin. That is not nothing. Obese people have a tough row to hoe under any circumstance and this just adds to it. Discouragement is probably the biggest problem with obesity and by itself definitely leads to a shorter life or is a more important drawback than longer life anyway.
Still it’s all just preaching.
1. T. Mehta D. L. Smith Jr. J. Muhammad K. Casazza. Impact of weight cycling on risk of morbidity and mortality. Obesity Reviews 2014;15(11):870-81.
2. Smith DL et al. Weight Cycling Increases Longevity Compared with Sustained Obesity in Mice. Obesity 2018;26(11):1733-39.
3. Di Germanio C et al. Yo‐Yo Dieting is Better than None. Obesity 2018;26(11):1573