News release

From: Adelaide University

Yo-yo dieters who struggle to lose weight and keep it off may achieve better results by following an intermittent fasting diet, rather than traditional calorie counting.

An Adelaide University study focusing on the psychological aspects of both intermittent fasting and calorie restriction, compared the effects both diets had on eating behaviours, mood, sleep and quality of life.

Although both diets led to similar amounts of weight loss, those on the fasting diet didn’t feel as though they needed to make major changes to their eating behaviours – such as monitoring overeating or counting calories - in order to lose weight.

This contrasts with the calorie restriction diet, where participants reported consciously having to think about restricting their food intake and avoiding overeating. That improved control accounted for 15% of their weight loss.

“While many diets can result in weight loss, they may be difficult to stick to and this makes keeping that weight off long-term more challenging,” said Professor Leonie Heilbronn from Adelaide University’s School of Medicine and the South Australian Health and Medical Research Institute.

“The results of our study indicate intermittent fasting could offer an alternative pathway for people who find conventional dieting challenging.”

More than 200 people with obesity were involved in the 18-month trial, which saw participants split into three diet groups – intermittent fasting, continuous calorie restricted and standard care

The intermittent fasting group was required to consume 30% of their energy needs between 8am and 12pm on three non-consecutive days each week, followed by a 20-hour fast. On non-fasting days, they were able to eat their regular diet.

Those on calorie restricted diets were limited to eating 70% of their usual diet, while the remaining participants followed standard diets but were given healthy eating guidelines.

Participants on both calorie restricted and intermittent fasting diets lost around seven kilograms in six months, compared to just two kilograms lost by those on the standard diet. They also reported improved levels of depression and wellbeing – even on fasting days.

The findings, which have been published in the journal Clinical Nutrition, suggest calorie restriction and intermittent fasting diets may drive weight loss through different psychological and behavioural pathways.

“Psychological and behavioural effects have a major influence on people’s abilities to adhere to diets. Intermittent fasting may help people achieve weight loss through ways that are less dependent on consciously restricting intake,” said Professor Heilbronn.

While intermittent fasting has become increasingly popular, relatively little is known about its long-term psychological and behavioural effects compared with standard dieting approaches.

“Future trials should be designed to identify individuals who struggle to improve eating behaviours, as they may do better with intermittent fasting diets, enabling more personalised weight management,” said Professor Heilbronn.