Despite their newfound popularity, diets that promote fasting every other day are no more effective than the traditional diet, based on research published in JAMA Internal Medicine.
Conducted at the University of Illinois, this study assessed a new weight loss fad called alternate-day fasting. As the name suggest, alternate-day fasting involves significantly cutting back on calories on “fast days” and indulging on “feast days.” The biggest draw is that dieters get a break between fasting, which many believe helps people stick to the diet. But how does it stack up against the traditional daily diet?
To learn more, researchers enrolled 100 overweight and obese adults into a randomized weight-loss study for one year. Participants were assigned to an alternate-day fasting diet, a traditional diet or no intervention at all. The alternate-day fasting group was instructed to consume roughly 500 calories on fast days and about 2,500 calories on “feast days,” while those on the conventional diet limited intake to about 1,500 calories every day.
The diets lasted six months and were then followed by a six-month weight-maintenance phase.
After analysis, researchers found that both diets were just as effective when it came to weight loss after one year. Compared to participants who stuck to their usual diets, participants on the alternate-day fasting diet lost about 6 pounds after one year while those in the conventional diet group lost an average of 5.3 pounds.
However, there were a few key differences between the groups. First, participants in the alternate-day fasting group were more likely to drop out of the study than those on the conventional study. Second, participants in the fasting group had significantly higher cholesterol levels than those on the conventional diet after one year. Participants in the fasting group were also more likely to exceed calorie intake on “feast days” and overly restrict intake on “fast days.” In comparison, those in the conventional group generally stayed within their guidelines.
Aside from these differences, other outcomes like blood pressure, blood sugar and markers of inflammation were similar among both groups.
The take-home message, according to authors, is that alternate-day fasting does not appear to be more effective than the traditional daily diet. Participants fasting every other day lost the same amount of weight as those who restricted their calories daily and, surprisingly, were more likely to drop out than those on the traditional diet.
However, that’s not to say alternate-day fasting may not be useful for patients struggling with weight loss. Alternate-day fasting appears to be effective and may be easier for patients who have trouble restricting their calories every day. Thus, experts hope that with future research, we can better understand the effects of alternate-day fasting on both weight loss and health.