April 21, 2022 -- Not so fast! Daily fasting while restricting calories may not help you shed more pounds than just cutting back on calories, a new study suggests.

Over the course of a year, study participants who ate only from 8 a.m. to 4 p.m. did not lose significantly more weight than individuals who ate whenever they wanted, nor did they see significantly greater improvements in other obesity-related health measures like body mass index, study author Deying Liu, MD, of Southern Medical University in China, and colleagues said.

Daily fasting has become more popular as a weight-loss strategy because it is easy to follow, which helps people keep it up, the authors wrote in the study published in the New England Journal of Medicine.

However, “the long-term efficacy and safety of time-restricted eating as a weight-loss strategy are still uncertain, and the long-term effects on weight loss of time-restricted eating as compared with daily calorie restriction alone have not been fully explored,” they said.

To learn more, Liu and colleagues recruited 139 adults with BMIs between 28 and 45. All participants were told to eat no more than 1,500 to 1,800 calories per day for men and 1,200 to 1,500 calories per day for women. To determine the added impact of fasting, participants were placed either in to a fasting or non–fasting groups. Patients in the fasting group ate only during an 8-hour window from 8 a.m. to 4 p.m., while the nonf-asting group ate whenever they wanted.

At 6 months and 12 months, participants were re-evaluated for changes in weight, body fat, BMI, blood pressure, and metabolic risk factors, including blood sugar levels, triglycerides, blood pressure, and others.

Limiting Calories May Explain Benefits

At 1-year, 118 participants remained in the study. Although members of the fasting group lost slightly more weight on average than those in the non-fasting group (average of 17.6 pounds vs. 13.9 pounds), the difference between groups was not statistically significant.

Most of the other obesity-related health measures also trended toward favoring the fasting group, but again, none of these improvements was statistically significant.

“We found that the two weight-loss regimens that we evaluated had similar success in patients with obesity, regardless of whether they reduced their calorie consumption through time-restricted eating or through calorie restriction alone,” Liu and colleagues concluded.

Principal investigator Huijie Zhang MD, deputy director of the department of endocrinology and metabolism at Nafang Hospital, said their findings are “consistent with the findings in previous studies.”

“Our data suggest that caloric intake restriction explained most of the beneficial effects of a time-restricted eating regimen,” Zhang said.

Still, Zhang called time-restricted eating “a viable and sustainable approach for a person who wants to lose weight.”