Alternate-Day Fasting May Have Same Results as Counting Calories


Fasting every other day or counting calories are weight loss techniques. The fasting sounds as if it would get the best results for anyone looking to lose weight, but according to a new study, either diet produces pretty much the same results.

In the study, researchers found that alternate-day fasting didn’t make that much of a difference in weight loss compared to people who counted calories. Both methods get weight loss results, said Krista Varady, lead author and professor of Nutrition at the University of Illinois in Chicago.

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“We basically showed that they both produce a clinically significant amount of weight loss,” Varady told CNN. “Instead of being better than calorie restriction, [fasting is] the same. So it’s kind of like an alternative to calorie restriction.”

The study participants included 100 metabolically healthy obese adults, with an average body mass index (BMI) of 34. The adults were randomized into one of three groups for a year: an alternate-day fasting group, a calorie restriction group and a control group that had no interventions.

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The year-long trial included a six-month weight loss phase before a six-month phase of weight maintenance, the study said. The alternate-day fasting group consumed 25 percent of energy needs on fast days, but consumed 125 percent of energy needs on the alternating “feast days.”

The calorie restriction group consumed 75 percent of energy needs on a daily basis. Eric Ravussin, co-author and a professor at the Louisiana State University Pennington Biomedical Research Center, said while the fasting diet might seem like a better option, it’s not always the case.

“Even if the weight loss was a primary end point, I think that the question is really: What is the best strategy to get people to stick to a diet?” Ravussin said. “We know daily calorie restriction – if you have to count your calories every day and all that – it’s a tough one. I think that there’s some hope that this alternate-day fast, or modified fast, would be a better or easier strategy, but … the dropout rate is kind of alarming.”

Only 69 participants dropped out of the study from the calorie restriction and control groups, but the alternate-day fasting group suffered the highest dropout rate. Varady said the results were surprising, since it seemed as if the fasting diet would be easier.

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“We were a little bit shocked to see that it was actually the calorie-restriction group that seemed like they could stick better to their daily calorie goals,” she said. “Instead of eating the 500 calories on the fasting days, they were eating a couple hundred calories more on those days.”

Credit: Craig Suinter/Flickr, CC BY-ND 2.0

Those who did drop out of the alternate-day fasting group seemed to revert to calorie restriction as the study went on, the authors said. The extreme diet didn’t seem to be compatible for those used to eating throughout the day, Varady said.

“Alternate-day fasting doesn’t seem to work very well in people who are frequent snackers. People who need to eat every two hours, they don’t tend to fare well on this diet, whereas people that just naturally tend to go a long period of time without eating, like four to five hours … those people actually tend to do much better,” Varady said.

“I really think people just need to find what works for them,” she said. “Not one diet fits everyone.”

The authors said that, based on the study results, alternate-day fasting seemed to be less sustainable for the participants. There might be a smaller group of individuals that find the diet successful, but for the most part, the pattern of energy restriction was too difficult to follow, the study said.

“I don’t think there’s anything magical to the [fasting] diet at all,” she said. “I think it’s just another way of tricking people into eating less food or helping people to kind of monitor how much food intake there is or how much food they’re taking in.”