Intermittent Fasting May Be Linked to Binge-Eating Behavior — Study
The latest science suggests there are dangers to intermittent fasting.
Proponents of intermittent fasting — in which people limit the hours they eat — claim it can help with everything from weight loss to brain health and longevity. While intermittent fasting may have some health benefits (though that science is still being teased apart), some experts are sounding the alarm about potential risks associated with the practice. Others have called into question whether the purported benefits of intermittent fasting are markedly different from the benefits of other kinds of diets. Inverse spoke to researchers about the potential risks of intermittent fasting and who should definitely avoid the practice.
Intermittent fasting and the risk of disordered eating
Intermittent fasting (IF) usually falls into one of four practices:
- Alternate day fasting, or ADF: As the name suggests, this type of IF alternates fasting one day with eating as you typically would the next.
- Modified alternate-day fasting: Instead of completely fasting one day and eating normally the next, you alternate eating only 25 percent of your regular diet every other day.
- Periodic fasting: People practicing periodic fasting will limit food to roughly 500 to 600 calories two days per week (and eat as you typically would the other five days a week).
- Time-restricted eating: In this type of IF, people limit their “daily eating window,” so they only eat during a six to 10-hour window of the day, ideally during the “active” phase of their day. One common version of time-restricted eating is called 16:8, in which people fast for 16 hours (including the time they sleep) and only eat in an eight-hour window of their choosing.
Researchers say one of the most significant risks associated with intermittent fasting is disordered eating.
A recent study in the journal Appetite looked at more than 300 college students’ eating behaviors. 23.5 percent of the study participants were currently practicing intermittent fasting, 16 percent had tried it in the past, and 61 percent had never done IF. The researchers found that the participants who had previously done intermittent fasting were most likely to have an episode of binge eating compared to those who had never fasted. Additionally, the participants currently practicing intermittent fasting tended to give themselves less “unconditional” permission to eat during their non-fasting windows.
Jordan Schueler, a Ph.D. candidate in the Department of Psychological and Brain Sciences at Texas A&M and one of the researchers on the study, tells Inverse that she was surprised to learn that past fasters of the three groups were most likely to engage in episodes of binge eating. That said, both past fasters and current fasters were more likely to have an episode of binge eating than those who had never fasted. Past intermittent fasters averaged 3.2 episodes, and current IF-ers averaged 2.8 episodes. Both figures were statistically significant compared to people who had never practiced intermittent fasting (who averaged 1.8 binge eating episodes).
“I think this supports the idea that once you start intermittent fasting, the eating behaviors or habits that you develop do not just go away if you stop doing it,” Schueler says.
A study published last year in the journal Eating Disorders also found an association between intermittent fasting and eating disorder symptomology. The study authors write, “Specifically, half of the men and women engaging in IF reported engaging in at least one objective and subjective binge episode over the past month. Alarmingly, around 25 percent of men engaging in IF endorsed self-induced vomiting, and 15.9 percent of women and 27.8 percent of men reported laxative use.”
Both studies were relatively small, the 2023 study had 300 participants, and the 2022 study had only 64; that said, the potentially dangerous behaviors associated with intermittent fasting should serve as a note of caution, especially for anyone with a history of disordered eating.
Schueler says, “more research is needed to really confirm our findings and to help better understand the underlying reasons why IF may be associated with disordered eating.”
Who should avoid intermittent fasting?
People with a history of disordered eating aren’t the only people who should avoid intermittent fasting. Indeed, anyone thinking about intermittent fasting should talk to their doctor before beginning such a regime, but it may be hazardous for certain groups.
Andrea Love, an immunologist, and microbiologist who works as an immunology consultant for the biotech industry and co-host of the Unbiased Science podcast, tells Inverse that intermittent fasting can result in “fatigue, low energy, lack of focus, and obviously hunger, but it can also lead to loss of muscle mass and delayed recovery if you are participating in any sort of activities, exercise or sports. Intermittent fasting is also associated with decreased endurance, so anyone engaging in anaerobic exercise probably shouldn’t be fasting.”
In addition to some athletes, intermittent fasting could be dangerous for anyone with issues regulating blood sugar. “So anyone so anyone with diabetes or who is taking insulin, anyone who is prone to one, or type two diabetics that are taking insulin, anyone who is prone to hypoglycemia, should probably not be intermittent fasting because your body is not regulating blood sugar as it should,” Love says.
Pregnant or breastfeeding people should also avoid intermittent fasting, as should anyone under the age of 18 and over the age of 75. Suzanne Salamon, associate chief of gerontology at Beth Israel Deaconess Medical Center, tells Harvard Health intermittent fasting may also be risky for people taking some medications for blood pressure, heart disease or anyone who needs to take medicine with food at a specific time of day. It may also be dangerous for people with chronic conditions like kidney disease or ulcers to begin intermittent fasting.
The murky clinical applications of intermittent fasting
While weight loss is often the most-cited reason for beginning intermittent fasting, “there's no evidence that intermittent fasting is more beneficial than caloric restriction-based diets, where you are just eating fewer calories on a day-to-day basis,” Love says. And there is some evidence that intermittent fasting may be less sustainable because of how rigid it happens to be.”
For example, a study published last year in the New England Journal of Medicine tracked two groups of people for 12 months: one group was on a calorie-restricted diet, and the other was practicing intermittent fasting. The researchers found “no significant differences between the groups in gains in body lean mass over the 12-month intervention period,” adding that there were no differences between the two groups’ blood pressure and that both groups had comparable improvements in glucose, lipid levels, and insulin resistance.
If you don’t have any of the risk factors outlined and your doctor is on board, intermittent fasting may be harmless. But as Schueler says, “A one-size-fits-all approach is something to be wary of. For example, while IF has shown some promise in reducing cholesterol for some people, that does not mean that it will help everyone, and the consequences — for example, disordered eating — may outweigh the benefits for some folks.”