The 5:2 diet is one of the most publicised and popular diets of modern times: everyone from Beyoncé to Benedict Cumberbatch has been on it, and with Dr Michael Mosley seeing a reversal in his own type 2 diabetes thanks to two 500 calorie fasting days a week, not to mention losing 20lb and spearheading studies to prove its efficacy, it seems hard to argue that there’s a better way to lose weight in this day and age.
Until, perhaps, now. A new study published in the International Journal for Obesity by the School of Health Sciences of the University of Tasmania suggests that a ‘two weeks on, two weeks off’ style of dieting could be more effective for sustained, successful weight loss than continuous dieting or intermittent fasting diets such as the 5:2. Here’s how researchers came to that conclusion, although further study is required to truly declare fortnightly diet plans as a superior mechanism of weight loss...
Professor Nuala Byrne and her team examined weight loss in a group of 47 obese men, ranging from 30 to 50. The men were split into two dieting camps: 23 maintained a continuous calorie restricted diet, with daily calorie intake reduced by a third, while the remainder adopted the same regime for two weeks, with a two week break. The study ran for 16 weeks, within which time the “fortnightly” dieters not only lost more weight overall, but were shown to have kept it off six months after the study had finished.
So just how does reduced deprivation lead to greater results? Professor Byrne attributes a lessened ‘famine reaction’ to the weight loss success of the ‘two weeks on, two weeks off’ diet:
“When we reduce our energy (food) intake during dieting, resting metabolism decreases to a greater extent than expected; a phenomenon termed 'adaptive thermogenesis' - making weight loss harder to achieve.”
Professor Byrne reported that, for reasons yet to be concretely identified, alternating two week dieting ‘shifts’ shows promise over alternative dieting methods
"There is a growing body of research which has shown diets which use one to seven day periods of complete or partial fasting alternated with ad libitum food intake, are not more effective for weight loss than conventional continuous dieting.
It seems that the 'breaks' from dieting we have used in this study may be critical to the success of this approach.”
Whether solely biological, or because two weeks of discipline is easier to maintain when you know you’ve got a fortnight of relative dietary freedom coming up, ‘two weeks on, two weeks off’ could well make a dent in the West’s obesity epidemic, but for the meantime, if the 5:2 works for you , that’s a goer too. As long as you’re eating a healthy, balanced diet overall and not cutting out food groups, it’s all good.