Q. Recently I have seen several college students who are regularly fasting. This seems risky. Do we have any information about the effects of fasting, especially among young adults with eating disorders?
A. Finding that young people are regularly fasting is not surprising. It is estimated that nearly 1 in 5 men and 1 in 4 women in college are regularly fasting, and these numbers are only increasing. Often this takes the form of a daily fast, where an individual eats one large meal per day and then fasts for the next 18 to 24 hours. Some do this to lose weight but others claim it improves their physical and mental functioning.
A recent article from the University of California, San Francisco, outlines some of the negative effects of this growing trend (J Eat Disord. 2021. 9:88). Data from the Healthy Minds Study, which surveyed 8255 college undergraduates and graduate school students, showed that the students who regularly fasted had high rates of depression, anxiety and, importantly, eating disorders, suicide ideation, and non-suicidal self-injury (cutting and burning themselves). Also increased were substance use disorders, including use of marijuana and illicit drugs such as ecstasy and cocaine.
Eating disorders were measured with the SCOFF, a 5-item questionnaire that asks such questions as “Do you ever make yourself sick because you feel uncomfortably full?” and “Do you worry that you have lost control over how much you eat?” Regular fasting during the past 4 weeks among men was significantly associated with positive depression, anxiety, and eating disorders screens. Among women, regular fasting during the past 4 weeks was significantly associated with greater odds of marijuana or illicit drug use in the past 30 days as well as positive results on depression, anxiety, and eating disorder screens.
Among college men and women, a higher body mass index was associated with any degree of fasting, which was no surprise because one of the primary reasons for fasting is weight loss. However, BMI was not associated with regular fasting. Among women who reported regular fasting, greater odds of cigarette smoking, marijuana use and use of other illicit drugs were reported.
In the popular press, fasting is presented as a health strategy. Sharing information about the risks associated with fasting with the students you are seeing may be helpful. Furthermore, the results from studies such as the one at the University of California-San Francisco may be helpful. Also, in studies such as this, it is not clear whether fasting causes eating, anxiety, mood and substance use symptoms or is promoted by them. But, either way, regular fasting is a reason for real concern.