Intermittent fasting has long been debated as a weight loss technique. Now a new study looks at how effective it is compared to daily calorie counting.
In the study, published Monday in the Annals of Internal Medicine, researchers monitored the weight changes among 125 participants in two groups: those who followed a daily caloric restriction diet and those who followed the 4:3 intermittent fasting diet, which consists of 4 unrestricted days and 3 nonconsecutive fasting days per week.
"On non-fast days, participants in the 4:3 intermittent fasting group did not have to restrict energy intake, but were encouraged to make healthy food choices," according to news release. On fasting days, they were to cut calorie intake by about 80%. Those in the calorie restriction group were given a daily goal of cutting their caloric intake by 34.3%.
Participants were aged 18 to 60 years old, with a range of body mass index, or BMI, of 27 to 46. (A BMI of 27 is in the "overweight" range, 30-39 is considered "obese" and over 40 is "morbidly obese.") Both groups were given free gym membership and encouraged to exercise for at least 300 minutes per week. They also received comprehensive behavioral support throughout the process, including calorie counting instruction and guidance on target dietary macronutrients.
After 12 months, results showed the intermittent fasting group saw greater reductions in weight than the calorie-counting group.
"Participants in the 4:3 intermittent fasting group had a -7.6% change in body weight compared to -5% in the calorie restriction group," the researchers reported. "58% of those in the fasting group achieved weight loss of at least 5% at 12 months vs 47% in the calorie restriction group."
Despite planning for the groups to have an equal calorie deficit, researchers determined people on the 4:3 intermittent fasting diet actually ended up eating less, leading to higher weight loss.
Still, there are different schools of thought behind fasting's effectiveness, nutritionist and dietitian Carrie Glassman told "CBS Mornings" on Tuesday.
"Many people and researchers that believe that the reason intermittent fasting works is because it's a simple way to restrict calories. Then there are researchers that say that it works because the body goes into this fasting mode, which helps you burn more fat and lose cat and lose more weight and also promote other health benefits," she said.
Plus, Glassman noted the exercise component is ciritical.
"Not just for weight loss, but actually to help maintain weight loss, exercise is always important," she said.
The study authors added that the fasting method may be appealing for dieters who don't want to worry about counting calories every day. Still, weight loss between the groups varied, exposing the need for more research.
"Future studies should evaluate biological and behavioral predictors of response" to both diet plans, "to provide insight for personalization," the authors added.
Fasting is also not an option for everyone, Glassman warned.
"It's not going to work for people with Type 1 diabetes, people with a history of eating disorders, people on certain medications (and) children," she said.
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Sara Moniuszko
Sara Moniuszko is a health and lifestyle reporter at CBSNews.com. Previously, she wrote for USA Today, where she was selected to help launch the newspaper's wellness vertical. She now covers breaking and trending news for CBS News' HealthWatch.