A new study finds that intermittent fasting three days a week can lead to greater weight loss and better health outcomes than daily calorie counting, with less daily effort.
A randomized clinical trial investigated whether 4:3 intermittent fasting leads to greater weight loss than daily calorie restriction when paired with comprehensive behavioral support in adults with overweight or obesity. Over 12 months, the 4:3 intermittent fasting group experienced modestly greater weight loss. The findings were published today (March 31) in the Annals of Internal Medicine.
A randomized clinical trial compared the effects of 4:3 intermittent fasting versus daily caloric restriction on weight loss when combined with comprehensive behavioral support in adults with overweight or obesity. The data showed that 4:3 intermittent fasting resulted in modestly greater weight loss over 12 months. The results are published in Annals of Internal Medicine.
Study Design: Fasting vs. Calorie Counting
Researchers from the University of Colorado School of Medicine and their colleagues enrolled 165 adults with overweight or obesity. Participants were randomly assigned to follow either a 4:3 intermittent fasting regimen or a traditional daily calorie restriction plan for one year.
Those in the intermittent fasting group followed a modified fasting schedule, reducing their energy intake by 80% on three nonconsecutive days per week. On the remaining four days, they could eat without strict calorie limits but were encouraged to make healthy food choices. In contrast, participants in the daily calorie restriction group followed a daily energy deficit of about 34.3%.
All participants received free gym memberships and were encouraged to exercise at least 300 minutes per week. Both groups also took part in group-based behavioral support and were given tools for calorie tracking along with dietary guidance targeting macronutrient goals: 55% carbohydrates, 15% protein, and 30% fat.
Results After 12 Months of Dieting
After 12 months, participants in the 4:3 intermittent fasting group lost an average of 7.6% of their body weight, compared to a 5% loss in the daily calorie restriction group. Additionally, 58% of those in the fasting group achieved at least 5% weight loss, versus 47% in the calorie restriction group.
The fasting group also saw more favorable changes in several cardiometabolic markers, including lower systolic blood pressure, improved cholesterol levels (total and LDL), and reduced fasting glucose.
According to the researchers, intermittent fasting may promote better adherence because it doesn’t require constant daily calorie tracking or restriction. They suggest it could be a viable, evidence-based alternative for weight management in adults with overweight or obesity.
Reference: “The Effect of 4:3 Intermittent Fasting on Weight Loss at 12 Months” by Victoria A. Catenacci, Danielle M. Ostendorf, Zhaoxing Pan, Laura K. Kaizer, Seth A. Creasy, Adnin Zaman, Ann E. Caldwell, Jared Dahle, Bryan Swanson, Matthew J. Breit, Kristen Bing, Liza T. Wayland, Shelby L. Panter, Jared J. Scorsone, Daniel H. Bessesen, Paul MacLean and Edward L. Melanson, 31 March 2025, Annals of Internal Medicine.
DOI: 10.7326/ANNALS-24-01631
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