Intermittent fasting can be hit or miss, but research suggests 'sweet spot' can help some stick to their diet
Cutting back on calories three days a week may lead to more weight loss than daily dieting and may be more effective than other types of so-called "intermittent fasting," a new study suggests.
In a new study published in the Annals of Internal Medicine, researchers asked participants to reduce their calorie intake by 80% of what their body needed to maintain weight on three non-consecutive days each week. On the remaining days, they had no calorie restrictions, but were still encouraged to make healthy choices.
Over the course of a year, people in the intermittent fasting group lost nearly 17 pounds—about 60% more than those who were asked to trim back their daily calories by one-third, according to the study.
This style of intermittent fasting "appears to be easier to adhere to over time," Dr. Victoria Catenacci, lead author of the study and an associate professor of medicine at the University of Colorado, told ABC News.
"It's really hard to restrict calories every day," she says. "It's just another strategy for people to consider."
Neither group hit their calorie targets, she noted, but those who fasted a few days a week ended up eating fewer calories overall and were more likely to stick with the plan.
Danielle Ostendorf, another of the study's authors and an assistant professor at the University of Knoxville, said she suspects that intermittent fasting hasn't shown this level of success in past studies because the number of fasting days was often too few or too many—making the plans either ineffective or hard to follow.
Fasting for three days, Ostendorf says, is "something like a sweet spot."
Participants also took part in a comprehensive lifestyle program focused on behavior change. They set exercise goals, attended frequent group meetings led by dieticians, and received personalized support.
The authors emphasize that the additional support made a big difference. "This program really provided accountability for the participants, and like social support. They were able to learn from each other," Ostendorf shared.
No participant reported any downsides to the diet itself. However, the study included only healthy adults and excluded people with serious conditions like diabetes.
The authors recommended that anyone considering this type of fasting talk to their doctor and a registered dietician. Joining a support group may also help with encouragement and accountability, they advised.
Dr. Amy Rothberg, an endocrinologist and director of the University of Michigan Weight Management Program, supports patients trying new diets as long as they still balance healthy foods. "If that's something that they think they can do, I'm all for it," she said.
"If you don't want to count calories, track and log your food intake," intermittent fasting "may be beneficial for some people," she said. Still, she stressed that people should choose diets they can stick with long-term.
The study did not track participants beyond one year to see if weight loss was maintained.
"There's no superior dietary approach," Rothberg said. "So you need to find an approach that is tailored to that individual."
Catenacci takes a similar view with her own patients, recommending a variety of strategies based on what someone is interested in.
"At the end of the day, the best diet for any given person is the one that they feel they can adhere to over time," Catenacci said.
Dr. Alice Gao, MD, MPH, is a family medicine resident at Temple Northwest Community Family Medicine and a member of the ABC News Medical Unit.
