Updated: Oct 20
When we think of fasting, many of us will jump to fasting practices for religious or perhaps political reasons. However, it is becoming increasingly popular to implement an ongoing fasting regime some days of the week for the potential health benefits, known as intermittent fasting (IF).
The 5:2 diet is perhaps the most popular and well known of these diets at the moment. On two non-consecutive days of the week, intake is restricted to approximately 25% of a persons energy needs, with normal or potentially increased intake on the other days.
Can Intermittent Fasting Improve our Health?
In a nutshell, yes. But is it better than a sustained but balanced calorie reduced diet? Not necessarily. The majority of research on intermittent fasting has been conducted on animals, however there have been some promising human trials.
The intermittent fasting diet has been linked to weight loss, reduced weight circumference and reduced cholesterol, but so can a sustained calorie restriction diet, so why do it?
Weight loss and improvements in cholesterol.
May feel less restrictive than sustained calorie restriction diets.
Can teach people about their hunger and fullness cues, so people can become more in tune with their body and needs.
Intermittent fasting is a very calorie focused dieting style, and it can be overwhelming and draining to be counting calories regularly.
There are a number of side effects that may put people off intermittent fasting, such as feeling tired, constipated, getting 'hangry' and getting headaches.
Studies on intermittent fasting have shown significantly higher drop out rates than people on continuous restriction diets, and any diet style that you can't maintain is ultimately not much use.
Intermittent fasting is not recommended for a number of people, for example anyone who is very active, pregnant or diabetic, as well as children, teens and people with eating disorders.
There have been no long-term studies to examine possible future effects of fasting diets, nor has anyone determined the optimal ratio of fasting:non-fasting days
Take home message
Intermittent fasting can be a useful diet style for some people who find continuous calorie restrictions too limiting, however there is no evidence to suggest it is any more successful than traditional sustained caloric restriction diets.
Remember that no one diet will suit everyone, but working with a dietitian has been proven to increase peoples ability to achieve their health goals.
"Intermittent Fasting", DAA Hot Topics, June 2017
Hankey, Klukowska and Lean, "A Systematic Review of the Literature on Intermittent Fasting for Weight Management", The FASEB Journal 2015.