Alternate-day fasting (ADF) had positive effects on body weight, cardiovascular measures, and molecular markers of aging when assessed in a randomized controlled trial among healthy adults without obesity or diabetes, researchers report in a study published online August 27 in Cell Metabolism.

ADF is a different approach to control weight than the common caloric restriction (CR) or intermittent fasting (IF) that restricts daily eating to an 8- to 12-hour window. Although ADF is gaining popularity it has not been subject to randomized clinical trials.

Therefore, Slaven Stekovic, PhD, from the Institute of Molecular Biosciences at the University of Graz in Austria, and colleagues conducted a prospective cohort study with an embedded randomized controlled trial to assess the metabolic effects of ADF. The team initially recruited 30 participants who had followed ADF for at least 6 months before the study began and compared them to 60 healthy controls. Thirty members of the control group were then randomly assigned to ADF for 4 weeks and the other 30 participants ate whatever and whenever they wanted during that time.

Specifically, the 30 people who had followed ADF for 6 months or more and the 30 individuals randomly assigned to ADF alternated between 36 hours of not eating and 12 hours of eating whatever they wanted. These two groups were similar in terms of gender distribution, age, body mass index (BMI), and waist-to-hip ratio at baseline.

Before and after the intervention, participants underwent a battery of anthropometric, physiological, hormonal, metabolic, and biochemical measurements that reflect health status and possible effects of ADF. These included measures of body composition and cardiovascular function, caloric expenditure assessed using food frequency and exercise questionnaires, and bone mineral density at the lumbar spine.

No adverse effects were seen among participants in the ADF group. Their caloric intake dropped from baseline by 37.4% (95% CI, –48.3% to –24.4%), compared with 8.2% (95% CI, –32.2% to 3.6%) in the control group.

BMI among the 4-week fasters fell by 1.2 kg/m² (95% CI, –1.515 to –0.875; P < .0001). The average reduction in belly fat was 14.5% ± 6.4% (P < .0001).

In addition to changes in body mass and composition, researchers noted metabolic trends, which is why they chose to publish in Cell Metabolism rather than a more general journal. “Cell Metabolism is very open to translational findings and there is probably no other intervention that changes the metabolism of an organism as profoundly as fasting,” co-author Frank Madeo, PhD, a professor at the Institute for Molecular Biosciences at the University of Graz in Austria, told Medscape Medical News.