Eat very little for a couple of days, then eat whatever you’d like for the rest of the week, and lose weight… Sounds easy, but if you’re seeking weight loss, does intermittent fasting stack up?
What is it?
The idea of reducing your kilojoule (energy) intake from food to lose weight is nothing new, and while fasting has been a part of many religions for centuries, doing so on some, but not all days of the week for health is a relatively new concept.
Popularised by diet programs like the ‘5:2 diet,’ a typical week of intermittent fasting might involve two (non-consecutive) days of eating around 25 per cent of your energy requirements, then eating normally on the remaining five days of the week. Other programs are more arduous, and suggest ‘fasting’ every second day.
Energy requirements are individual, based on factors like height, age, gender, and activity level. But in general, a fasting day involves eating and drinking around 2,000 – 3,000 kilojoules worth of food and drinks. To put this in context, two boiled eggs, a slice of wholemeal toast, and an apple amount to around 1,000 kilojoules, so it’s clear to see a fasting day wouldn’t involve much food.
What does the evidence say?
Supporters of intermittent fasting point to weight loss, and improvements in risk factors for chronic disease, like reduced cholesterol, as reasons to follow the diet. But while the current body of evidence tells us that while intermittent fasting diets may lead to weight loss, it’s unlikely they’re superior to a standard balanced reduced-kilojoule diet.
Research presented at DAA’s 2016 National Conference compared the 5:2 diet to a standard reduced kilojoule diet, amongst a small group (24) of obese male war veterans. After six months, researchers reported both groups lost weight, and reduced their waist circumference, but there was no significant difference between the two groups.
Interestingly, weight loss slowed at the three-month mark for both groups, which was when dietitian follow-up tapered out, showing support may be the key element in continuing success.