An alternate-day fasting diet didn’t do better at curbing weight loss than a more traditional calorie-restricting one – but that doesn’t mean you should throw it away like that extra helping of chocolate cake.
According to a new small study published in JAMA Internal Medicine, people who followed an alternate-day fasting diet didn’t have significantly divergent weight loss results than those under a daily calorie restriction.
Researchers looked at 100 obese adults – 86 women and 14 men – from October 2011 to January 2015 as part of the trial. For one year, patients were put into separate groups. An alternate-day fasting group would eat 25 percent of their calorie needs on so-called “fast days,” followed by 125 percent on a “feast” day. Another group only ate 75 percent of their calorie needs per day, while the final group didn’t receive any diet intervention.
The study found an average weight loss of 6 percent in the alternate-day fasting group compared to 5.3 percent in the daily calorie-restriction group. The results didn’t match the study’s hypothesis, which sought to determine how effective the diet would be.
Diet adherence turned out to be better in the calorie-restriction group, even though the alternate-day group got to eat whatever they wanted every other day.
Study author Krista A. Varady stressed to U.S. News that this doesn’t rule out the diet as a viable option. Even on the feast days, the participants ate less than they would typically eat. Varady thinks this is why they lost the same amount of weight.
“It’s not really a negative result,” Varady, of the of the University of Illinois at Chicago, said. “This diet just doesn’t happen to do better than a traditional approach, but it still is an effective diet for weight loss.”
Not everyone completed the study, with the largest dropout rate coming from the alternate-day fasting group at 13 out of 34 people, compared to 10 out of 35 in the daily calorie-restriction group and 8 out of 31 in the control group.
“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,” according to the study. “Nevertheless, it is still possible that a certain smaller segment of obese individuals may prefer this pattern of energy restriction instead of daily restriction. It will be of interest to examine what behavioral traits (ability to go for long periods without eating) make alternate-day fasting more tolerable for some individuals than others.”
Could this diet be for you? If you can go for five to six hours without eating, Varady says you have a better shot compared to those who need to eat every two to three hours. She added that no diet will suit every person.
Study limitations included that the maintenance phase was only a short six months, researchers didn’t give as much attention to the control group as the others and the alternate-day group’s dropout rate might have posed selection bias, among others.
Varady says that in some pilot findings coming out, the alternate-day fasting diet seems to work better in terms of reducing insulin resistance and triglycerides and increasing HDL cholesterol (aka the “good” kind). The JAMA study focused on otherwise healthy obese people.
