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December 10, 2019

What is Intermittent Fasting?

What is Intermittent Fasting?

Intermittent fasting is having its moment.

Silicon Valley executives have considered it a type of biohacking, a productivity hack that may optimize human performance. Today hosts Jenna Bush Hager and Hoda Kotb have publicly committed to a month-long trial of it. And for many people admonishing themselves for the holiday cookies and candy, they’re enjoying this season, it’s sure to be a 2020 New Year’s resolution.

Yet, despite the many entertainment news segments, celebrities, and water-cooler chats about intermittent fasting, there remains much to learn about the increasingly popular “health” trend.

What is intermittent fasting?

As the name suggests, intermittent fasting is an eating pattern that alternates between periods of fasting and eating. Participants limit their eating to a certain window of time—to just eight hours per day, for example, or five days per week—and abstain for the remainder of the time. Sometimes called “time-restricted eating,” this approach focuses more on the timing of the meals (and fasts) than on the quantity or nutritional value of the foods consumed.

Proponents of intermittent fasting cite an array of benefits, from longevity to mental clarity to a reduced risk of cancer, Alzheimer’s, and heart disease. Arguably the most talked-about and celebrated possible effect, however, is weight loss. According to the International Food Information Council Foundation, intermittent fasting was one of the most common diets of 2019, and over half of the dieters surveyed cited weight loss as the primary reason for beginning their own diets.

Dangers of intermittent fasting

Often missing from conversations about intermittent fasting is a nuanced look at its potential dangers. As is so common in diet culture, the weight loss associated with the trend is celebrated as a universal good. The general public considers it a worthwhile pursuit in the name of health, promoting it before research has established its efficacy, sustainability, or safety.

Indeed, though fasting has existed in religious traditions and scientific studies throughout history, research on modern-day fasting practices is limited. In their review of human and animal studies about intermittent fasting published in Behavioral Sciences, Harvie and Howell (2017) conclude that the long-term benefits or harm remain unknown:

“We do not know conclusively whether long-term IER [intermittent energy restriction] is a safe and effective method of weight control for subjects who are overweight or obese or whether IER may confer health benefits to people of any weight independent of weight loss.”

The majority of studies on intermittent fasting include only small sample sizes tracked over a short span of time. And while many report a measurable physiological outcome like short-term weight loss, they generally ignore any mental and emotional health effects.

Several reports do concede that fasting “may not be for everyone,” but the disclaimer is largely an afterthought—a generic recommendation to “check with a professional before starting any diet plan.” As we nod to the fact that any alleged benefits of intermittent fasting cannot be generalized, it is also important to more thoughtfully consider the risks.

Intermittent fasting and eating disorders

Given the more established research on eating disorders, including their signs, symptoms, and risk factors, it is worth exploring how intermittent fasting may be associated with these illnesses. The trend may be especially harmful for those experiencing, recovering from, or at risk of developing an eating disorder. Intermittent fasting may amplify or conceal disordered behaviors, inhibit eating disorder recovery, and increase the likelihood that an individual may develop a severe eating disorder.

  1.  Intermittent fasting may amplify or conceal disordered behaviors.
    Under the guise of intermittent fasting, individuals may conceal restrictive behavior and thereby delay the identification and treatment of a disorder like anorexia, bulimia, or binge eating disorder.
  2.  Intermittent fasting may inhibit recovery.
    Eating disorder recovery aims to reconnect individuals with their bodies—to tune into hunger cues and intuitively support their bodies with the food they need. Intermittent fasting and other external food rules may further distance recovering individuals from the bodies they’re learning to trust.
  3.  Intermittent fasting may contribute to the development of an eating disorder.
    Though eating disorders have no single cause, a key risk factor is dieting. Those who lose weight by fasting intermittently may make themselves more susceptible to developing a severe eating disorder.

Given the prevalence and severity of eating disorders, it is essential that we critically analyze the conversations about intermittent fasting and other restrictive eating plans. If you or someone you love is struggling with food, please schedule an eating disorder assessment with The Emily Program today. Get started online or call us at 1-888-364-5977 to discuss treatment options.


Harvie, M. & Howell, A. (2017). Potential benefits and harms of intermittent energy restriction and intermittent fasting amongst obese, overweight and normal weight subjects: A narrative review of human and animal evidence. Behavioral Sciences, 7(1): E4. doi: 10.3390/bs7010004.

International Food Information Council Foundation (2019). 2019 Food and Health Survey. Retrieved from

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