Nine in 10 health club members admit to having regular “cheat days” – when they allow themselves to indulge on treats and unhealthy food and drink.

A survey by health food retailer Musclefood, which studied more than 3,000 UK fitness enthusiasts, revealed that 87 per cent of respondents regularly gave in to their cravings for high fat and high-calorie treats such as takeaways, burgers and ice cream.

The poll also shows that predetermined cheat days are used widely as a reward for working out in the gym. Some even build cheat days into their workout plans in order to use them as motivation to make it to the gym on the other days of the week.

A spokesman from Musclefood.com said: “The results of our survey show just how challenging it can be for even those who understand exercise and diet to stay on message and stick with a healthy eating plan all the time.

“It seems the majority of those who work out treat themselves to regular cheat days. While there is nothing wrong with this theory, we would urge caution and recommend people keep a close eye on their intake, even during these cheat days.

“It’s ok to have the occasional treat or reward but it shouldn’t be an excuse to binge eat. If you are struggling to make gains in the gym it could be a good idea to look at your eating plan honestly and maybe reappraise those cheat days a little.”

The poll also shows that while a majority (56 per cent) of fitness fans make a point of eating at least five portions of fruit and veg every day, only 13 per cent claimed to stick with their clean living lifestyle throughout a typical week.