Intermittent fasting shows modestly greater weight loss than daily caloric restriction,reveals study

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.

Researchers from University of Colorado School of Medicine and colleagues randomly assigned 165 adults with overweight or obesity to either 4:3 intermittent fasting or calorie restriction for 12 months to compare weight loss between interventions. Participants in the 4:3 intermittent fasting group undertook a modified fast to produce an 80% energy restriction for 3 nonconsecutive 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. Participants in the calorie restriction group were prescribed a daily calorie goal designed to produce a 34.3% energy deficit. All participants were given a free gym membership and encouraged to exercise for at least 300 minutes per week. In addition to group-based behavioral support, participants received instruction in calorie counting and a guide to target dietary macronutrient content of 55% carbohydrates, 15% protein and 30% fat.

At 12 months, participants in the 4:3 intermittent fasting group had a –7.6% change in body weight compared to –5% in the calorie restriction group. 58% of those in the fasting group achieved weight loss of at least 5% at 12 months vs 47% in the calorie restriction group. Participants in the fasting group also achieved more favorable changes cardiometabolic outcomes including systolic blood pressure, total and low-density lipoprotein cholesterol levels, and fasting glucose level. According to the authors, the findings suggest that because fasting does not require participants to focus on counting calories and restricting food intake every single day, it may result in greater adherence and should be considered within the range of evidence-based dietary weight loss approaches.

Reference:

Victoria A. Catenacci, Danielle M. Ostendorf, Zhaoxing Pan, et al. The Effect of 4:3 Intermittent Fasting on Weight Loss at 12 Months: A Randomized Clinical Trial. Ann Intern Med. [Epub 1 April 2025]. doi:10.7326/ANNALS-24-01631.