News Release

Intermittent fasting may not be as safe as once believed

Popular dietary trend is linked to dangerous eating disorder attitudes and behaviors among adolescents and young adults

Peer-Reviewed Publication

University of Toronto

Intermittent fasting, described as fasting for greater than 8 hours at a time, is a dietary trend that continues to grow in popularity. While it is purported to positively affect one’s long- and short-term health, and many use this behavior to control or lose weight, few have examined its potential harms. A new study published in the Eating Behaviors aimed to fill this research gap. 

Analyzing data from over 2,700 adolescents and young adults from the Canadian Study of Adolescent Health Behaviors, researchers found that intermittent fasting was linked to all disordered eating behaviors for women, including binge-eating, and compensatory behaviors like vomiting and compulsive exercise. Among men, those who engaged in intermittent fasting were more likely to report compulsive exercise.    

The prevalence of intermittent fasting behaviors among adolescent and young adults was notable. In total, 47% of women, 38% of men, and 52% transgender or gender non-conforming individuals reported engaging in intermittent fasting in the past 12 months.    

“Given our findings, it is problematic how prevalent intermittent fasting was in our sample,” says lead author Kyle T. Ganson, PhD, MSW, assistant professor at the University of Toronto’s Factor-Inwentash Faculty of Social Work.    

In all three groups, participants reported an average of 100 days where they engaged in intermittent fasting over the past 12 months.   

“The associations found between intermittent fasting and eating disorder behaviors are particularly salient, given the significant increase in eating disorders among adolescents and young adults since the start of the COVID-19 pandemic,” says Jason M. Nagata, MD, MSc, assistant professor at the University of California, San Francisco, and a study co-author.     

The findings provide a warning to healthcare professionals about recommending intermittent fasting as a means of weight loss, as it may facilitate eating disorder attitudes and behaviors.    

“We need more education in healthcare settings and greater awareness in popular culture, including social media, of the potential harms of intermittent fasting,” says Ganson. “At this point, the proposed benefits are still unclear and unsupported by research, and the potential harms are becoming clearer.”   

Visit for more information on the Canadian Study of Adolescent Health Behaviors 

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