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Alternate-Day Fasting Is Tough To Stick To And No Better Than Simply Cutting Calories, Says Study


Tom Hale

Tom is a writer in London with a Master's degree in Journalism whose editorial work covers anything from health and the environment to technology and archaeology.

Senior Journalist


Alternate-day fasting is the fad diet of the moment, with celebrities and mere mortals alike swearing by its miraculous ability to shed pounds. This method of dieting involves “fasting” for one day, when people consume notably fewer calories than normal, alternated with a “feast” day, when they can eat more calories than normal.

Over the past decade, this diet has become increasing more popular, no doubt thanks to its endorsement from celebrities like Beyonce and Hugh JacksonSmall studies in the past, both on labs rats and humans, have also suggested it could be beneficial for your health.


However, a randomized clinical trial has weighed in on the debate and claims that the alternate-day fasting isn’t significantly better at losing weight than simply cutting down on calories. It is, however, harder to sustain.  

The study, published in JAMA Internal Medicine, followed 100 obese adults for over three years, in what the researchers say is one of the longest and largest trials of alternate-day fasting to date.

They randomly assigned the participants three different diets: no intervention, cutting down on calories every day by 25 percent, or alternate-day fasting (25 percent of calorie needs on fast days, then 125 percent of calorie needs on alternating "feast" days).

"The results of this randomized clinical trial demonstrated that alternate-day fasting did not produce superior adherence, weight loss, weight maintenance or improvements in risk indicators for cardiovascular disease compared with daily calorie restriction," the authors concluded.


After one year of the diet, the researchers found that the alternate-day fasting group's weight loss was not significantly different from the daily calorie restriction group – 6 percent and 5.3 percent of their body weight on average, respectively. Changes in blood pressure and heart rate were also not significantly different between the two groups.

Crucially, they also found that the dropout rate for the alternate-day fasting group (38 percent) was higher than that in the daily calorie restriction group (29 percent). This was due to higher numbers of the fasting group being dissatisfied with their diet and so not adhering to it strictly: eating slightly more than allowed on fasting days and slightly less on cheat days.

“Taken together, these findings suggest that alternate-day fasting may be less sustainable in the long term, compared with daily calorie restriction, for most obese individuals,” the authors claimed. “It appears as though many participants in the alternate-day fasting group converted their diet into de facto calorie restriction as the trial progressed.”

In terms of losing weight, different people suit different things. As the study shows, alternate-day fasting can provide results. However, since it’s barely more effective and hard to stick to, they argue many obese people might find it easier to use other methods of dieting. It’s all just about making an informed decision about what’s best for you.


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