Yo-yo dieting doesn't necessarily make you heavier in the long run

Many of us have lost weight to feel better about our bodies before donning a bathing suit for a beach holiday, or getting into that just-too-tight outfit for a special occasion.

But old habits die hard, and before we know it we’ve started eating that chocolate cake and stopped going to the gym. Soon after losing the weight, we find ourselves back where we started – or worse. This is called yo-yoing.

Our research, published recently in the journal Preventive Medicine, set out to investigate whether yo-yoing results in more weight gain long term. It did for women who started out at a healthy weight, but not for women who were obese.

Is any weight loss better than none?

For the growing number of us who are overweight, any weight loss is good. Losing just 5% of our body weight (4kg for an 80kg person) leads to improvements in blood sugar levels, blood pressure, and cholesterol. We also feel better about ourselves.

But if we lose weight, we lose muscle. Then when we regain weight, we gain more fat than muscle. Muscle burns more energy than fat, which makes it harder to lose the weight the next time.

Repeat this cycle a few times, and it could mean we gain more weight over time.

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There is also another worry that yo-yoing of weight may affect how we feel about ourselves. We could become demoralised because we’ve failed. This was found to be the case in a study from Finland, which found associations between yo-yoing and poor mental health.

Long-term impact

Our new study found 40% of women had one to two episodes of yo-yoing, which we classified as intentionally losing 5 kg and then regaining this amount. We asked that question 12 years ago, so it’s probably higher now since obesity is affecting more people.

Our study looked at nearly 10,500 Australian women (aged 47 to 52 years) who had more than three cycles of yo-yoing. We compared them to women who had not yo-yoed. We also looked at how their weight and their mental health changed 12 years later.

We found women who had an unhealthy weight at the beginning of the 12-year period (who were classified as obese) and had yo-yoed did not put on more weight than women who had never yo-yoed.

This means the benefit of losing weight remains, even if you put it back on from time to time. Being lower weight at some points is helpful for your health, and doesn’t mean you will put lots of weight back on.

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Things get more complicated if we’re talking about women who were a healthy weight to begin with and yo-yoed. These women seemed to gain weight over the long term.

It could be that these women are using unhealthier practices that may eventually result in greater weight gain, such as laxatives. Laxatives are short-term solutions for weight loss and cannot be continued.

Overall, women who yo-yoed a lot also seemed to be more depressed, and this could be caused by the discouragement of failing to keep the weight off.

How to keep the weight off

If you’re a yo-yoer and tend to regain that weight, focus on the positives: you’ve already benefited from being at a lower weight, and that’s great for your health. And you did it once, which means you can do it again.

To maintain your lower weight next time, evidence suggests regular weighing can help. Then, you can monitor small lapses and make necessary changes to diet and activity.

Also, since exercise improves mood, keep it up when you try to lose weight and as you maintain your lower weight. This will help keep you positive.

Beyond that, keep in mind everybody is unique so it’s important to try different things until you find what works for you. Then, make it your new habit.

Read more: You don't have to be the biggest loser to achieve weight loss success

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.