Intermittent fasting is not always healthy, may lead to disordered eating, study finds

• Intermittent fasting includes fasting for specific periods, ranging from fasting during certain hours of the day to particular days of the week.

• Evidence is mixed about the health benefits of intermittent fasting.

• New research from a diverse study found that intermittent fasting is associated with a higher prevalence of eating disorder behavior and psychopathology, particularly among young women.

• Some people can practice intermittent fasting if they keep certain safety tips in mind.

Intermittent fasting (IF) is a popular diet trend among health and fitness enthusiasts, which involves not eating during planned intervals of time.

While intermittent fasting may offer some health benefits, researchers are still working to understand the full impact of this eating pattern.

A recent study published in Eating Behaviors looked at the practice of intermittent fasting among adolescents and young adults in Canada.

The researchers found an association between intermittent fasting and the behaviors and psychopathology of eating disorders and other dangerous behaviors among some members of this age demographic.

The results indicate a need for more research into the potential risks of intermittent fasting.

Benefits and drawbacks of intermittent fasting

Intermittent fasting can take on a few different forms.

A typical example of IF is fasting for 2 non-consecutive days in the week.

Another method would be to only eat during certain times of the day. For example, the 16/8 method involves fasting for 16 hours and eating during only an 8-hour window.

Blanca Garcia, RDN, a Los Angeles-based registered dietitian nutritionist and nutrition specialist with the Measurement Instrument Database for Social Sciences (MIDSS), not involved in the study, noted the potential benefits of eating within certain time frames to Medical News Today:

“With proper guidance from a registered dietitian, a client can be guided into choosing well-balanced foods within the method of 16:8; I like this method because it’s basically eating three meals within a workday. A chronic dieter may skip meals or avoid many good foods.”

Some evidence suggests that intermittent fasting can contribute to weight loss and provide certain health benefits.

Intermittent fasting may help to improve insulin sensitivity and heart health. It may also aid in preventing disorders like Alzheimer’s disease and cancer.

However, there are potential drawbacks to intermittent fasting.

For instance, intermittent fasting may increase the risk of hypoglycemia and could induce muscle wasting if someone isn’t getting enough protein.

For certain people and groups like young children and older adults, fasting could be dangerous and should be avoided.

In addition, many aspects of the possible drawbacks of intermittent fasting still haven’t been studied.

Disordered eating and intermittent fasting

For the present study, researchers examined the relationship between intermittent fasting and eating disorders among adolescents and young adults.

This study gathered data from the Canadian Study of Adolescent Health Behaviors.

Researchers included 2,762 adolescents and young adults in their analysis, including women, men, and transgender or gender non-conforming individuals recruited via social media.

Researchers found that intermittent fasting was highly popular in this age demographic.

Study author Kyle T. Ganson, Ph.D., MSW, assistant professor and Factor-Inwentash Faculty of Social Work with the University of Toronto, Canada, explained to MNT:

“IF [Intermittent fasting] was highly common among the sample, including 48% of women, 38% of men, and 52% of transgender/gender non-conforming participants, and participants fasted for, on average, 100 days in the past 12 months.”

Researchers used an eating disorder examination questionnaire to examine behaviors and psychopathology. They wanted to see how these attitudes and patterns were similar to those of people with eating disorders.

The questionnaire looked at participants’ dietary restraints and concerns about weight, shape, and eating. They also looked at eating disorder behaviors, like binge eating, compulsive exercise, and laxative use.

“Among all groups (men, women, and transgender individuals), any engagement in intermittent fasting (IF) in the past 12 months was associated with greater eating disorder attitudes and behaviors,” Ganson explained.

“Additionally, among women, in particular, IF was associated with all eating disorder behaviors, including binge eating, vomiting, laxative use, and compulsive exercise, while among men, IF was associated with compulsive exercising.”

The findings indicate a need for further research into the potentially harmful effects of intermittent fasting, particularly among young people.

Study limitations and continued research

While the new research provides insight into some potential dangers of intermittent fasting, it did have several limitations.

First, the study cannot determine whether intermittent fasting causes eating disorders or the other way around.

In addition, the data collection methods relied heavily on participants’ self-reporting, which can lead to potential errors. And while the sample was diverse, there is still the potential for selection bias based on the methods used.

There was also the possibility for participants to interpret the survey questions differently, increasing the risk of response bias. Finally, the questions may not have captured all eating disorder cognition and behaviors.

All these limitations indicate the need for further research into this area.

Despite these challenges, healthcare professionals can still glean insight. Ganson noted a few clinical implications of the research:

“The data from this study indicates that IF may be problematic and associated with severe and harmful eating disorder attitudes and behaviors. Healthcare professionals need to be aware of these potentially correlated behaviors, as well as understand contemporary dietary trends like IF that are commonly discussed among young people, particularly on social media. Thus, more comprehensive assessments need to be conducted among young people related to dietary practices and proper guidance [given] when necessary.”

Engaging safely in intermittent fasting

People in some groups should not engage in intermittent fasting, such as those who are immunocompromised or people with certain hormonal imbalances.

The results from this study indicate the potential dangers of intermittent fasting among young adults and adolescents.

Still, some people may engage in intermittent fasting safely by understanding the facts and gathering careful insight from professionals. It’s also important to understand that everyone has different needs and risks.

If you’re interested in trying intermittent fasting, Garcia recommended the following tips to stay healthy:

• Meet with a registered dietitian who can teach you about good food choices.

• Choose a method that gives you nutrition daily.

• Avoid bingeing on high calorie foods and fast foods, but rather, incorporate what you like in small doses daily. (e.g., if you like cookies, 1 or 2 cookies a day is OK).

Non-study author and registered dietician Anastasia Gialouris, CDN, a certified dietitian nutritionist in Brooklyn, New York, offered a few safety considerations to keep in mind:

 “Those who choose to give intermittent fasting a try should still aim to consume adequate balanced meals during their limited eating window, full of whole, minimally processed foods, to ensure they get enough nutrients into their bodies. Secondly, since hunger and low energy are two of the main side effects of intermittent fasting, it is vital to listen to your body. If you are fasting and you reach a point of extreme weakness [or] dizziness, then please eat something, even if it is just a small nutritious snack to get you by.”

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