Eight-Hour Diet: Dietician Explains How It Does (And Doesn't) Work

Stock image of woman holding clock
Stock image of woman holding clock

Over the past few years, fasting has taken the world of dieting by storm, with experts claiming the process can do everything from kickstarting your metabolism to encouraging speedy weight loss while allowing you to eat exactly what you want during periods of non-fasting.

But what's the truth behind The 8-Hour Diet?

According to the American diet book published in 2013, written by the bestselling “Eat This Not That” author David Zinczenko and Men’s Health editor-in-chief Peter Moore, it is possible to reset a dieter's metabolism by introducing fasting or 'fat-burning' periods. During this time, the body will lose weight.

Outside of these periods, for eight hours at each stretch (such as between 9am to 5pm or 11am to 7pm) dieters are free to consume as many calories and whatever type of food they desire -- and they will still shed those extra pounds.

HuffPost UK Lifestyle spoke to Azmina Govindji from the British Dietetic Association (BDA):

:: Do you think this diet concept really works and what are the potential pitfalls?

In practical terms, the conscious thinking that goes into planning the week helps to engage your brain. When you do this, you are more aware of what you are eating and this conscious awareness could help you to be more careful on non-fast

days, which can result in an overall reduction in calories over the week, helping you to lose weight.

The idea of not having to exercise restraint is alluring and can be helpful – as soon as you tell yourself you can’t have a food, you want it even more, so the idea of being able to eat what you like is a very positive message.

But we need to ensure that fasting isn’t taken to the extreme and that foods eaten provide the nutritional balance needed to carry on with life as usual and prevent low levels of key micronutrients.

Long term weight management is about finding a healthy lifestyle that you can keep to, won't get bored of, and that meets your nutritional requirements.

The BDA recommends a balanced lifestyle of varied foods that provide essential nutrients as well as behaviour change that is sustainable in the long term. It is unlikely that this is a sustainable approach and it tends to fuel a dieting mentality – dieting doesn't lead to long term weight loss; it's a healthy relationship with food rather than food deprivation that will help you keep the weight off in the long term.

Far better to set yourself realistic goals of 5-10% weight loss with a slow steady approach than to go for a faddy eating plan.

:: Do you agree people should eat whatever they want in unlimited quantities, within certain time periods, while trying to lose weight?

This doesn’t help build an empowering eating behaviour with control over cravings. It doesn’t inspire you to make nutritious food choices – rather, it sounds like you can eat all the junk you like, so long as it’s within the 8-hour limit.

It doesn't steer you towards long term habits that will help you keep the weight off once you “come off the diet”.

However, to their credit, the authors do appear to promote lean protein foods, nuts, yogurt and some whole grains.

:: Is it true that human bodies are incapable of properly processing food after the set eight hours, which results in extra pounds ending up in places they shouldn’t, specifically the abdomen and hips?.

Your weight loss depends on your calorie deficit over the week /month. Weight change revolves around calories in (ie food) vs calories out (ie activity) and effects of this diet regime are mediated via their impact on calorie intake vs calorie expenditure. In the end, if you take in fewer calories as food than you use up in your daily activity, you will lose weight, period.

Like any topical diet, this diet lures people by the promise. We live in a society of quick-fixes and trying out something sensational focuses you on a new eating pattern – and this newness can be motivating.

:: Is our 24-hour eating culture responsible for the high rate of overweight people in society?

There’s more to our obesity crisis than this. Low levels of activity, hidden fat and sugar in foods, takeaways, high calorie snacks and portion sizes are a few reasons.

:: Could intermittent fasting help to prevent diabetes, heart disease, kidney disease, and Alzheimer’s?

There is some research on the effect of fasting on health and theories include the switching on of “repair genes”, and beneficial effects against aging and certain diseases. Like all areas of research, some of the science is stronger than others.

:: Researchers have found that when men fasted every other day for two weeks, the insulin in their bodies became more efficient at managing blood sugar. Do you think fasting could solve diabetes crisis?

This is an interesting area and more research is needed on humans (much of it is in mice) before we can see this as a sensible long term eating plan for managing blood glucose.