Can fasting diets help you to lose weight?

Recent headlines reported that “fasting diets” are no more effective for long term weight loss than standard daily dieting. These headlines were reporting on a US study that used alternate-day fasting to help people lose weight. The US study took men and women who were overweight or obese to compare weight loss with either a daily low calorie diet (25% of their normal intake) or an alternate-day fasting diet where they were asked to have 25% of their usual calories on “fast” days, and 125% on the following “feast” days, the remaining third were asked to continue to eat normally.

The study showed that those on the alternate-day fasting diet and those on daily diet lost roughly the same amount of weight (5-6%) after six months compared to those who weren’t on a diet.



Participants found the alternate-day fasting regime as difficult to keep to as a daily diet and ended up eating more than advised on their “fast” days and less than advised on their “feast” days. The Research Dietitians here at Prevent Breast Cancer welcome this study, particularly as it looked at the long term sustainability of a fasting diet.

The ability of people to adhere to a regime is a crucial aspect of any diet. However, it is important to highlight that this study was testing an alternate day fasting diet which is only one type of fasting diet. The findings don’t necessarily hold for other types, such as the 5:2 diet or 2 day diet. The study showed that the fasting diet was equally as good as standard daily dieting, so fasting diets may work well for some people.

There is no one-size fits all approach to dieting, the key is to figure out what works well for each individual.