New Study Reveals Intermittent Fasting Can Have These Dangerous Side Effects

 There is a fair share of benefits to intermittent fasting (IF)—a diet where you eat only within a limited window of time (generally 8 hours) and fast for the remaining hours of the day. IF has become a popular option for those who aim to improve their health via their diet as one of these benefits includes weight loss. However, a new study has found that this eating pattern can lead to dangerous side effects.

The new study, which was published in the journal Eating Behaviors, involved an analysis of data from the Canadian Study of Adolescent Health Behaviors. Taking into consideration information regarding more than 2,762 adolescents and young adults, the findings showed that over the course of one year, 38.4% of men, 47.7% of women, and 52% of transgender or gender non-conforming individuals had used intermittent fasting.

Those behind the study discovered that intermittent fasting was significantly associated with disordered eating behaviors. For women, that included binge eating and vomiting as well as compulsive exercise, while men tended to engage in the latter.

"Given our findings, it is problematic how prevalent intermittent fasting was in our sample," said lead author Kyle T. Ganson, Ph.D., MSW, assistant professor at the University of Toronto's Factor-Inwentash Faculty of Social Work, according to EurekAlert!

Jason M. Nagata, MD, MSc, a co-author of the study and assistant professor at the University of California, San Francisco, added, "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." 

"The study shows an association that we already see in practice," Mary Curnutte, MS, RD, LD, of the Louisville Center for Eating Disorders, tells Eat This, Not That! "Clients often start the practice of intermittent fasting to 'be healthy' as this is something promoted as healthy. However, restricting our intake can lead to other extreme eating behaviors. Ignoring hunger can cause hunger to build, resulting in overeating and binge eating. These behaviors can also trigger compensatory behaviors such as over-exercise or vomiting."

"Additionally, those prone to restrictive eating disorders can find that the restriction in intermittent fasting will then trigger these restrictive urges," Curnutte says. "I am glad to see a study that uses a large data set to show that these associations are significant, so we can communicate to others that intermittent fasting is something to be careful about."

Curnutte also notes that "those with a history of an eating disorder should never intermittent fast under any circumstance." Additionally, "those who feel they have a tricky relationship with food should avoid this as well."

For others who are interested in intermittent fasting, Curnutte says, "Our bodies naturally fast overnight. When giving yourself an overnight food break, our bodies will see these fasting benefits. If someone decides they would like to intermittent fast for a time longer than our natural overnight fast when we sleep, I encourage them to discuss it with a Registered Dietitian to make sure they are not missing a key component that may harm their body."