Intermittent Fasting: More mentally harmful and less physically beneficial than claimed?

Intermittent Fasting and Disordered Eating

Intermittent fasting is an eating pattern that limits food intake to specific time periods each day. There are various IF schedules, each differing in the length of fasting periods, ranging from several hours to an entire day. While intermittent fasting has gained popularity as a weight-loss strategy and is often promoted for its potential health benefits, research on its mental health effects remains limited. Recently, studies have begun exploring how intermittent fasting may be linked to disordered eating behaviors, raising important questions about its impact beyond physical health.

When studying the impact of intermittent fasting on mental health, researchers examine various aspects of disordered eating, such as an intense focus on thinness or muscularity, and how these behaviors affect daily life. Disordered eating refers to symptoms commonly associated with eating disorders but does not indicate a specific diagnosis. Instead, it provides a broader way to understand patterns of unhealthy eating behaviors.

On the other hand, intuitive eating describes eating patterns that encourage you to listen to your internal hunger cues to decide when and how much to eat. Intuitive eating includes eating for physical rather than emotional reasons—in contrast to binge eating, for example—and unconditional permission to eat—in contrast to restrictive or compensatory eating disorder behaviours, which rule over the “permission to eat” with certain “terms and conditions” that must be met before or after eating. The behaviours involved in intuitive eating are not only the mirror-opposite of disordered eating symptoms, but also may promote psychological well-being.

A recent study explored how intermittent fasting affects intuitive eating, BMI (body mass index), and disordered eating over time.

How the Study Was Done

Psychologists from universities in China and the US used online surveys to ask 491 Chinese adults about their eating habits and attitudes. The survey was taken twice: once at the beginning (Baseline) and again 8 months later (Follow-up). The average age of participants was about 30 years old, and half of them were male.

The surveys included questions about eating, BMI, and intermittent fasting. To measure intermittent fasting, the surveys asked respondents to choose between the options: “Yes, I am currently engaging in IF,” “Yes, I have attempted IF in the past, but have since stopped doing it,” or “No, I am not currently engaging in IF and have not attempted IF in the past.” To allow BMI calculations, the surveys asked for the height and weight of each respondent. To measure disordered eating behaviours and attitudes, the surveys included questions about thinness-oriented disordered eating, muscularity-oriented disordered eating, and harmful impacts of disordered eating on their daily life. The surveys also included a typical assessment of intuitive eating.

At both timepoints, each respondent was asked the same set of questions. Collecting responses at two timepoints allowed the psychologists to look for both cross-sectional findings (comparisons between-groups at one time) and longitudinal findings (comparisons over time).

Key Findings

The results of this study showed important cross-sectional and longitudinal findings.

To make cross-sectional comparisons, the researchers sorted the respondents into three groups based on their intermittent fasting answer: Current Intermittent Fasting, Past Intermittent Fasting, Never Intermittent Fasted. The baseline survey responses to the other questions were compared between these three groups.

• The Current Intermittent Fasting group had significantly higher thinness-oriented disordered eating scores than the Past Intermittent Fasting group.

• The Never Intermittent Fasted group had the lowest thinness-oriented disordered eating scores and the highest intuitive eating scores.

• At baseline, the Current Intermittent Fasting group also had highest muscularity-oriented disordered eating and daily life impairment scores.

After 8 months, the groups were compared again for longitudinal findings. Compared to the people who at baseline reported Never Intermittent Fasting…

• The people who at baseline reported Current Intermittent Fasting or Past Intermittent Fasting had significantly higher muscularity-oriented disordered eating and daily life impairment scores in the follow-up survey.

• The people who at baseline reported Past Intermittent Fasting had significantly higher thinness-oriented disordered eating scores in the follow-up survey.

• The people who at baseline reported Past Intermittent Fasting had significantly increased BMI, and significantly lower scores on the “unconditional permission to eat” part of the intuitive eating survey, in the follow-up survey.

What These Findings Mean for Intermittent Fasting

These findings challenge the idea that intermittent fasting is a reliable strategy for long-term weight loss and raise concerns about its potential impact on eating behaviors and mental health. The study found that people who engaged in IF tended to have higher BMI, more disordered eating behaviors, and lower levels of intuitive eating. This suggests that, rather than being a simple solution for weight management, IF may be linked to unhealthy eating patterns.

However, it’s important to consider the study’s limitations. The researchers relied on a single question to assess intermittent fasting habits, meaning they couldn’t capture details like how often, how long, or what type of fasting people were practicing. Additionally, all the data came from self-reported surveys, which can sometimes be inaccurate—especially for sensitive topics like weight and eating behaviors.

Another key point is that this study found correlations, not causes. In other words, people who fasted were more likely to have certain eating patterns, but that doesn’t necessarily mean fasting caused those patterns. Finally, the study focused on highly educated Chinese adults in a non-clinical setting, so more research is needed to see if these findings apply to other groups.

Overall, these results highlight the need for further research into how intermittent fasting affects eating habits and mental health.

Does this study resonate with you? Does this research make you think differently?

If it’s happened to you, it matters. Whether you’ve fasted, binged, restricted, or struggled with food rules—your experience belongs in this conversation.
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Link to the scientific paper: He, J., Chen, X., Cui, T., Xiao, Y., Barnhart, W.R., Wang, Y., Yi, S. and Nagata, J.M. (2025), Engagement in Intermittent Fasting is Prospectively Associated With Higher Body Mass Index, Higher Eating Disorder Psychopathology, and Lower Intuitive Eating in Chinese Adults. Int J Eat Disord, 58: 225-237. DOI: 10.1002/eat.24322.