Fasting vs. anorexia

What is the difference between fasting and anorexia?

Fasting and anorexia are quite different, but their qualities may overlap to create confusion. Anorexia nervosa is an officially recognized mental health disorder, and fasting or intermittent fasting is a method of consuming energy.^1,2

Understanding anorexia nervosa 

Anorexia nervosa is a psychological condition marked by the severe restriction of calories, flawed body perceptions, and an intense fear of gaining or not losing weight. People with AN will go to unhealthy lengths to try and reduce their weight while only eating small amounts of low-calorie foods.²

Over time, anorexia nervosa can result in many unwanted outcomes like:²

• Erratic or stopped menstruation
• Dizziness and fainting
• Weakness and muscle loss
• Gastrointestinal issues, like constipation, bloating, or feeling very full
• Bone fractures
• Mental health complications, like depression, anxiety, and poor concentration

Anorexia nervosa, like other eating disorders, may also result in serious medical complications. People can damage their heart, kidneys, and other organs by restricting their food intake.²

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Unpacking fasting and intermittent fasting 

Intermittent fasting is a planned method of eating that focuses on eating during specific windows of time. During the fast, a person will consume no food and only low-calorie beverages, like water, coffee, and tea. 

Some common forms of IF include:³

• 16/8 method - where a person fasts for 16 hours each day and eats their food during an 8-hour stretch of time.
• 5:2 approach - where a person eats typical meals for five days and fasts for two consecutive days. During fasting, the person could consume very few calories, up to one 500-calorie meal.

Fasting has become popular due to the perception of positive outcomes. But it’s important to note that fasting may be helpful for some, but that does not make it appropriate for everyone. (5) People may engage in fasting to:^1,3

• Lose weight
• Manage blood sugar
• Improve cardiovascular health
• Boost memory and mental clarity

Even though these health benefits may be possible, fasting and intermittent fasting may also create some risks. Anyone interested in exploring fasting, whether for weight loss or other benefits, should consult their medical team to make an informed decision.

When are restrictive diets considered disordered eating?

Restrictive diets are considered eating disorders when the intensity, frequency, or duration of the diet becomes problematic. When a person displays additional concerns linked to anorexia, bulimia, or binge eating disorder, it could signal an issue.

A restrictive diet may lead to disordered eating behaviors when:²

• Body weight becomes dangerously low
• Purging through vomiting, laxative use, or exercise occurs in addition to restriction
• Uncontrollable binges happen when not fasting
• The diet is affecting their relationships
• eating habits are hidden or feel shameful

Can fasting cause anorexia or another eating disorder?

Restrictive diets and disordered eating share a two-way relationship. Following a restrictive diet, like IF, can lead to someone developing an eating disorder, and people with eating disorders may point to restrictive diets to justify or normalize their unhealthy habits.^4,5

A 2022 study found a significant link between IF and eating disorders. People who used IF were likelier to display thoughts and behaviors associated with eating disorders.⁴