• Posted April 1, 2025

Fasting Outperforms Calorie Cutting, Clinical Trial Says

Fasting every other day can prompt more weight loss than simply cutting calories, a new clinical trial shows.

People who undertook 4:3 intermittent fasting lost just under 8% of their body weight within a year, compared to a 5% loss among people who cut their daily calories by about a third, researchers reported March 31 in the Annals of Internal Medicine.

In 4:3 intermittent fasting, people restrict their calorie intake by 80% three days a week, alternating between days with no dietary restrictions at all.

“Long-term adherence to daily calorie restriction is challenging for many people,” wrote the research team co-led by Danielle Ostendorf, an assistant professor of kinesiology, recreation and sport studies at the University of Tennessee Knoxville.

“Our results suggest that 4:3 [intermittent] is an alternative dietary weight loss strategy that may produce modestly superior weight loss compared with [daily calorie restriction] at 12 months, when provided in the context of a high-intensity, comprehensive behavioral weight loss program,” the team concluded.

For this trial, researchers assigned 84 overweight and obese people to this type of fasting, and another 81 folks to cut their calories by 34%.

Both groups were asked to get in 300 minutes of moderate-intensity exercise a week, double the amount recommended by U.S. physical activity guidelines. They also received support from a weight-loss program led by a registered dietitian.

After a year, the research team compared how the two groups did, and found that those who fasted lost slightly more weight on average.

However, those who fasted had better odds of achieving the sort of weight loss that produces health benefits, researchers found.

About 38% of fasting participants lost at least 10% of their body weight by the end of the year, compared 16% of those who cut calories, the study says.

More people were able to stick with fasting. Nearly 30% of those assigned to calorie cutting dropped out of the study, compared with 19% of those in the fasting group, results show.

Folks who fasted also tended to take in fewer calories overall, and had more improvements in blood pressure, cholesterol levels and blood sugar.

“Alternative patterns of restricting dietary energy intake for weight loss are gaining attention due to the difficulty of adhering to a reduced-calorie diet on a daily basis,” researchers wrote.

“An appealing feature of [intermittent fasting] is that dieters do not have to focus on counting calories and restricting intake every day as they do with daily calorie restriction,” they continued. “Furthermore, the periodic nature of fasting may mitigate the constant hunger associated with [daily calorie restriction].”

More information

The Cleveland Clinic has more on fasting.

SOURCE: Annals of Internal Medicine, March 31, 2025