Do diet 'cheat days' work – or do they backfire?

Trigger warning: This article references weightloss and disordered eating. If you are concerned about disordered eating, help and support is available.

If you've dieted or seen 'what I eat in a day' #WIEIAD videos online, you'll have heard of the concept of a 'cheat day'.

It's the idea that you can 'cheat' for one day a week as long as you stick to your chosen diet plan for the remaining six days.

While people diet for a range of reasons – from losing weight to gaining muscle or improving their sporting performance – it can be hard to know if this approach is a social media fad or actually works.

While cheat days may help some people stick to a plan, for others they can encourage overeating or an unhealthy relationship with food – especially when they can include very large portions of foods. So what's the appeal?

One reason why people choose to adopt this all-or-nothing approach to dieting is the theory it boosts your metabolism, causing you to burn more calories.

When you restrict your calorie intake, your body eventually adapts and resets your metabolism to your new lower intake, but the argument goes that cheat days reduce or prevent this.

The problem? "There is no rigorous scientific research to support this," says nutritionist Fiona Hunter.

Another popular theory is cheat days can help you stick to your diet by keeping your levels of leptin, external up.

Leptin, nicknamed 'the hunger hormone', is responsible for suppressing feelings of hunger. When you you diet, levels fall and this can make it harder to resist eating.

But can cheat days actually help keep your leptin levels up? Again, Hunter flags the lack of scientific evidence.

"Whether leptin has a role to play in controlling body weight is still a subject of debate among scientists, and the evidence that leptin actually increases after a cheat day is inconclusive", says Hunter.

Personal trainer Scott Laidler agrees: "Someone who is following a meal plan or getting in shape for the first time shouldn't be scheduling huge meals."

Some people use the day as an incentive or a treat – aka "something to look forward to", says Laidler. This might sound like a more positive, psychological framing but it still alludes to some foods being good and others bad.

"Some foods are more nutritionally dense than others", says sports and eating disorder dietitian Renee McGregor, external, but food isn't just good or bad, and needs to be "repackaged" to add other elements, such as enjoyment.

"It's how much and how often you eat it that counts", says Emma Randall, a mindful eating consultant.

The more you restrict some foods, the more you'll think about them – so plans built around cheat days can be harder to stick to.

Randall suggests a moderate weight-loss diet is likely to be better for your physical and mental health than a very restrictive diet with cheat days.

A recent medical review, external of the physiological and psychological response to cheat days found evidence that following a strict diet then 'rewarding' with a cheat meal may be linked with the behaviours of an eating disorder.

And while there might be benefits in some circumstances, the review says, ultimately this approach 'poses risks of fostering unhealthy eating patterns'.

More studies are needed for safer strategies around sustainable weight loss.

Laidler has seen how different plans can work for different people. "There are two types of people when it comes to dieting", he says, "those who need to let off steam in exchange for the discipline, and those who feel a sense of achievement from adhering to a plan".

He says letting off steam can work, as long as your cheat doesn't include lots of foods high in saturated fat, salt or sugar.

A scientific review, external suggested the most effective strategy for long-term weight loss and heart health is a diet that's compatible with what you like to eat and your lifestyle.

Hunter agrees, promoting flexibility rather than strict diets. "When I'm asked, 'What's the best type of diet to help you lose weight', my reply is always the same: 'the one you can stick to'."

Originally published March 2020. Updated March 2026

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