Another happy side-effect that can be triggered by intermittent fasting is weight loss. It’s typically the number one reason people turn to fasting in the first place.

The Cons of Intermittent Fasting

As with most things, and especially true with diets, there are always negative side-effects as well as positive ones.

“For most people, intermittent fasting is generally safe and beneficial,” says fellow Doctor 4 U GP Dr Diana Gall. “However, for those who are already fit and lean prior to fasting, there is a risk of hormonal imbalances which can cause problems with sleep.”

If this is the case, Dr Gall recommends careful monitoring by your GP. “If you have a health condition or you are taking medication such as blood pressure tablets, intermittent fasting can be dangerous,” she adds.

Diabetics can experience hypoglycaemia (low blood sugar) as a result of fasting and it’s not recommended for people with high calorie needs such as those underweight, under 18 or pregnant.

“There is also an argument that fasting for a long period of time encourages overindulgence when it’s time to eat,” adds Dr Gall. This can lead to binge eating and overconsumption when it is time to break your fast.

Not only can this undermine weight loss efforts, it can reinforce harmful habits in people who have previously had eating disorders or those at an increased risk of developing them.

How To Work Intermittent Fasting Into Your Routine

Rather than following a restrictive intermittent fasting diet year round, Dr Hyvernat prefers to prescribe a personalised three-day intensive “reset plan” done at a maximum of two to four times a year.

This way you can reboot your digestive system when it’s suitable for your schedule and means you aren’t locked into a long-term, inflexible plan.

While Dr Hyvernat urges caution and medical supervision before diving head first into a restrictive intermittent fast, others, such as the outspoken online PT James Smith, believe the whole trend should be taken with a big pinch of salt.