If you’re considering intermittent fasting to lose weight or improve your health, you’re looking to your future. But your past also plays an important role in the success – and safety – of your plan.
For people with a history of eating disorders (such as anorexia, bulimia, or binge eating disorder), diets of any kind – including intermittent fasting – aren’t recommended as they could trigger a resurfacing of these conditions that threaten your mental and physical health.
Even without that history, experts warn that intermittent fasting may trigger disordered eating behaviors in some people. So while it may have the potential to help with some medical conditions, it should only be prescribed by health care providers who are trained to carefully consider who it’s OK for and who might be at risk.
So says Samantha Hahn, PhD, MPH, an assistant professor, eating disorder epidemiologist, and registered dietitian at Central Michigan University in Mt. Pleasant, MI. She and her colleagues wrote in Clinical Diabetes and Endocrinology in 2023 that medical providers may recommend intermittent fasting as a treatment for chronic conditions, but these diets sometimes do more harm than good by triggering disordered eating habits.
Here, Hahn discusses the link between intermittent fasting and eating disorders, the signs that someone's fasting plan is veering into dangerous territory, and her recommendations.
Keep in mind:
- There are many forms of intermittent fasting, also called IF, some of which are more restrictive than others. These include plans where you fast for a certain number of hours per day or on certain days of the week. At their most extreme, they severely limit calories or when you can eat.
- Disordered eating and eating disorders aren’t the same thing. Disordered eating is a broader term for irregular eating behaviors (such as skipping meals, restricting certain food groups, skipping social events to avoid eating in front of other people, and guilt around foods). Eating disorders are medical conditions that include anorexia nervosa, bulimia, and binge eating disorder.
“Anyone who has an eating disorder engages in disordered eating, but not everyone with disordered eating meets the criteria for an eating disorder,” Hahn says.
This interview has been edited for clarity and length.
Q: First, what made you interested in looking at the connection between intermittent fasting and eating disorders?
Hahn: What we’ve found in the field is that a lot of disordered eating behaviors are normalized, especially on social media. It’s interesting to see what the latest trends are in dietary intake and the recommendation for what is “healthy” and whether or not it is actually health-promoting or not. This is especially true when it comes to people in larger bodies where disordered eating patterns are often celebrated. Intermittent fasting has been really popular over the last few years, so it’s important to acknowledge the potential negative consequences of such diet trends, particularly when it comes to potentially increasing the risk of disordered eating.
Q: Why has there been an explosion in intermittent fasting?
Hahn: Fad diets have changed over time. It used to be that fat was bad. Then carbs were bad. And now we’ve turned to intermittent fasting as the latest trend. I think this is a result of what is sometimes referred to as "moral healthism." People think that they should be striving for health and although not true, people equate weight and health. And so we’re continually striving for information on how to eat the “healthiest” and lose weight the quickest. Intermittent fasting promised a lot of that to a lot of people.
Q: Intermittent fasting isn’t just considered a fad diet. It’s often recommended by doctors for improving health in people who have certain chronic diseases, like type 2 diabetes. What is the problem with this given as a blanket recommendation?
Hahn: Any time we try to give blanket advice, it’s generally not effective. In particular, my worry with IF is that it’s extremely restrictive. This restriction is problematic for a number of reasons. Going long hours of the day without eating is a form of short-term starvation. This increases the likelihood of binge eating. You feel so hungry that you have a hard time regulating food intake again because your brain and body say, ‘I’ve gone a long time without food, I’m not sure when I’m going to get food again,’ which triggers the primitive part of your brain to eat more food.
Q: Can this increase the risk of developing disordered eating behaviors?
Hahn: Whether a diet promotes a defined period of eating or cuts out specific food groups, any time we see restrictions so broadly, that raises red flags for me as potentially increasing the risk of an eating disorder.
With intermittent fasting, there’s the thought that it’s not “good” to eat during a certain period. This moralizing leads to other problems, like thinking foods are “good” or “bad” or what eating patterns are “good” or “bad.” We get messages that we shouldn’t listen to or trust what our body is telling us. This sets people up for overly restrictive food rules and increases the likelihood of binge eating or disordered eating.
IF itself can be considered disordered eating. When we assess an individual for disordered eating, we ask about fasting or skipping meals because we know those behaviors are associated with negative physical and mental health consequences.
Q: Does this risk exist for people who don’t have a history of an eating disorder?
Hahn: For intermittent fasting specifically, I wouldn’t say that there’s great longitudinal evidence yet. What we know is that dieting is one of the most potent predictors of developing disordered eating, even if you’ve never had disordered eating before. It’s the restriction that is a risk factor. So I think on a population level, it’s very possible that engaging in IF could increase risk for later development of an eating disorder.
Q: How can someone use diet to improve their health without turning to restrictive methods?
Hahn: My philosophy as a dietitian is focusing on what makes our bodies and mind feel good, and what we can add, rather than what we can subtract. So instead of labeling food as “good” or “bad” or purposely cutting out certain foods because we “should,” trying to get in tune with our bodies' natural cues and identifying the types of foods that make us physically feel better, and focus on prioritizing those.
We also want to dive into the inner reasons why someone wants to make these changes to their diet. And finally, we want to correct misinformation, such as the idea that highly restrictive diets are effective or safe and that weight loss should be the goal.
Q: As you point out in your research, regular eating is a treatment for disordered eating and eating disorders. Tell us more about that.
Hahn: The best treatment we have is to help someone start eating more regularly so we can get them in tune with their body. Consuming nutrients in more regular intervals and quantities throughout the day helps with physiological and emotional regulation.
Eating at consistent intervals tells your body that food is a regular thing. That helps you learn your hunger and fullness cues. But we can’t do that until we’ve convinced our bodies that food at regular intervals will happen.
It’s good to speak with someone trained in nutrition who can assess what approach is right for them. Getting advice from a registered dietitian is preferable, though not everyone has access to one. As an alternative to any diet or restriction, I recommend looking at intuitive eating, which is more sustainable long-term.
Q: Where do we go from here so that medical advice to go on a specific diet doesn’t cause harm?
Hahn: I would advocate for universal screening. Disordered eating is incredibly underdiagnosed, particularly in certain populations, such as people of color, as well as individuals in larger bodies, of low socioeconomic status, and those who are gender-diverse. We need a universal screening process to assess everyone to see if they’re struggling and at risk for engaging in disordered eating.
When I’m teaching physicians, I advise deemphasizing weight. The current, standard practice assumes that weight equals health, which is not true. It also assumes that weight is a behavior, which it’s not. The current standard for a myriad of health conditions or anyone in a larger body is to tell the patient that they need to lose weight, but we know that it’s incredibly stigmatizing and it puts a lot of the responsibility for someone’s weight on them when we know it’s largely outside of their control.
We know that when people engage in health-promoting behaviors their weight may or may not change. And if they don’t lose weight, they’re often blamed for it. They may turn to disordered eating behaviors to lose weight. Weight is not a behavior, but we treat it like it is.
So instead of focusing on weight, let’s focus on behaviors that help no matter what like improvements in fruit and vegetable intake, physical activity, and a healthy relationship with food. Those things help disease states irrespective of weight but set people up for success rather than failure and stigmatization.
