Hi my fitness friends! This month I want to address Intermittent Fasting (IF) pros and cons relating to mental health. There is a lot of evidence-based research, some flawed, some not, some only in animal studies and not enough anecdotal observations (that I have seen in practice over a decade). It’s been all over the map. I would like to marry the two (real life and studies) to provide some insight and practical considerations before embarking on this fasting journey. When observing my own habits and what has worked for my body, I have noticed that in fact, I do fast anywhere from 12-17 hours based on my schedule or how I am feeling with food needs. I have naturally done this without force and alongside natural circadian rhythm cycles connected to the sun and moon. For instance, the last food intake by 4pm to eating again at 6:30am. For me, this has been natural based on my sleep-wake cycle (following a 5-year-old!) from 9:30pm to 5:30am. 

We will journey through some history, studies, and the effect of Intermittent Fasting on mental health. 

Intermittent Fasting Research

Intermittent fasting is commonly defined as the total abstinence of energy-containing food and beverages for 12-36 hours. Some people love it, and other people tend to fall apart when they give it a try. Some have even observed that intermittent fasting is one of the many causes of eating disorders.

Scientific interest in IF grew as part of investigations into aging and lifespan and was deemed part of The Longevity Diet by Professor Longo from the University of Southern California School of Gerontology. Importantly, these diet interventions also focus on non-refined carbohydrates, sufficient protein largely from plant-based sources, and most plant-based fats. Fasting by itself is not responsible for the longevity benefits, but is part of a lifestyle overhaul.

According to Longo: “the longevity diet is not a dietary restriction intended to only cause weight loss, but a lifestyle focused on slowing aging, which complements standard healthcare and taken as a preventative measure, will aid in avoiding morbidity and sustaining health into advanced age.” There is a difference between eating for longevity and dieting for weight loss.

Then IF became popular in weight-loss research and in fitness circles. Here comes good ol’ “diet culture” which can be defined as the pervasive assumption that appearance and body shape are more important than physical, psychological, and general well-being. It makes sense that not eating would cause weight loss, right? Let’s take a deeper dive and then put it into the context of eating behavior and mental health.

What the Research Says

Much of the research on IF is from animal studies, but some findings with human subjects in the last 10 years have increased interest for additional studies. Studies have highlighted associations between IF and weight loss, fat loss, improved cognitive function, increased longevity, and effects on diseases such as diabetes and certain types of cancer.

Studies also have examined whether circadian rhythm eating is beneficial, as I was mentioning earlier on. An Intermittent Fasting study conducted at the University of Alabama suggests that eating in alignment with the body’s circadian clock may positively influence health in several ways. According to researchers, metabolism functions at its optimum capacity in the earlier hours of the day, which suggests that eating in an earlier morning window would produce better weight loss outcomes.

Intermittent Fasting and Health Markers

Several trials have demonstrated that IF can cause weight loss in study duration periods from 8 weeks to one year. Among individuals with higher weights, IF shows short-term benefits for cardiometabolic outcomes such as low-density lipoprotein cholesterol, total cholesterol, triglycerides, fasting plasma glucose, fasting insulin, insulin resistance, and blood pressure. 

These conclusions have led to widespread press coverage of IF as a beneficial diet intervention for medical-related goals. But what happens over the long term? And what about mental health and our long-term relationship with food?

Intermittent Fasting and Mental Health

It has been suggested that some forms of time-restricted feeding may benefit mental health by improving brain signaling, neurogenesis, and synaptic plasticity. These outcomes can occur when overall calories and overall nutrients are not reduced. In other words, strategies of “chrononutrition” are used to improve circadian rhythms by altering sleeping and eating patterns. For example, it’s been discovered that the gut microbiota, that is, the microorganisms that live inside us, are circadian coordinators of metabolism, immunity, and mood. This is a very different conversation than diet culture’s common focus on weight loss and fitness. When will we also focus on our inside just as much as our outside??

Most studies showing the benefits of intermittent fasting on outcomes such as brain health and longevity are in animal models, which lack the connection to modern-day living. There are so many other factors to consider in everyday life that often get ignored in limiting biomedical models of nutrition. Context is so valuable!

Intermittent Fasting and Eating Disorders

In both animals and humans, fasting can lead to binge eating. In humans, fasting can lead to an obsession with food, which can lead to impairments in social functioning as well as emotional distress. In fact, an IF plan can look identical to a binge eating disorder (BED). One person might be engaging in time-restricted feeding without any binge eating, and the next can be restricting their food all day, binging at night, and calling it “IF.” The difference between these two individuals likely has to do with their psychological profile, level of body satisfaction, and the role of dietary restraint. IF and BED can look identical. This is quite worrisome, don’t you think?

It’s really helpful to discern between IF used to stabilize circadian rhythms, versus IF driven by dietary restraint, often generated from body dissatisfaction. 

In practice, it is common to see adverse outcomes associated with IF often. Most frequently, IF leads to loss-of-control eating and disruptions in social activities involving eating. In the short-term, many successful fasters report feeling better because they get the illusion of control over their appetite. But in the long term, the hunger can rebound and be ravenous, leading to feelings of failure and disappointment. Most notably, people who fast for only weight loss reasons often end up experiencing food cravings with more intensity, which can feel like a “food addiction” when it is oftentimes just because of the deprivation.

Bottom Line

I typically don’t recommend IF for weight loss, but I do for a nighttime fast going alongside natural circadian rhythm for the sake of optimal sleep, inflammation, and gut microbiome support (in the absence of any Eating Disorders or Disordered Eating history, of course). If the interest in fasting comes from body dissatisfaction and is geared toward weight loss, it is likely to compromise your relationship with food over the long run and is highly discouraged. If you have benefitted from being more strategic with “when” you eat, and it hasn’t caused problems, go with it!

Fasting may have some benefits for people who are not susceptible to developing eating disorders. For anyone with any history of any mental health diagnosis, fasting is generally not wise. This is also true for people searching for stress-eating help and searching for food neutrality. If fasting has led to signs of an eating disorder, please reach out for help. There are so many resources out there for you. The priority is healing the relationship with food and body. 

 There comes a time in the wellness journey when the best thing to do is tune out “diet culture” and the influencers who may be different from you. Does this resonate?

Let’s figure out how to cultivate your own unique style of nourishing that fosters holistic health. 

Miriam Jirari MPH, RDN, CPT, Intuitive Eating Counselor
Studio SWEAT Dietitian 

References: 

1. https://www.todaysdietitian.com/newarchives/JJ21p46.shtml 
2. https://wisemindnutrition.com/blog/intermittent-fasting-and-mental-health 
3. https://www.youtube.com/watch?v=9bsi4z5xlnM 
4.  Welton S, Minty R, O’Driscoll T, Willms H, Poirier D, Madden S, et al. Intermittent fasting and weight loss: Systematic review. Can Fam Physician Med De Fam Can. 2020;66(2):117–25.
5. Patikorn C, Roubal K, Veettil SK, Chandran V, Pham T, Lee YY, et al. Intermittent Fasting and Obesity-Related Health Outcomes. Jama Netw Open. 2021;4(12):e2139558.
6.  Currenti W, Godos J, Castellano S, Mogavero MP, Ferri R, Caraci F, et al. Time restricted feeding and mental health: a review of possible mechanisms on affective and cognitive disorders. Int J Food Sci Nutr. 2020;1–11.
7.  Alvarez Y, Glotfelty LG, Blank N, Dohnalová L, Thaiss CA. The microbiome as a circadian coordinator of metabolism. Endocrinology. 2020;
8. Zheng D, Ratiner K, Elinav E. Circadian Influences of Diet on the Microbiome and Immunity. Trends Immunol. 2020;
9. Chellappa SL. Circadian misalignment: a biological basis for mood vulnerability in shift work. Eur J Neurosci. 2020;
10. Avena NM, Rada P, Hoebel BG. Evidence for sugar addiction: Behavioral and neurochemical effects of intermittent, excessive sugar intake. Neurosci Biobehav Rev. 2008;32(1):20–39.
11. Kreisler AD, Mattock M, Zorrilla EP. The duration of intermittent access to preferred sucrose-rich food affects binge-like intake, fat accumulation, and fasting glucose in male rats. Appetite. 2018;130(Neuropsychopharmacology 22 4 2000):59–69.
12. Cuccolo K, Kramer R, Petros T, Thoennes M. Intermittent fasting implementation and association with eating disorder symptomatology. Eat Disord. 2021;1–21.
13. Lowe MR, Whitlow JW, Bellwoar V. Eating regulation: The role of restraint, dieting, and weight. Int J Eat Disorder. 1991;10(4):461–71.
14. Hockey A, Barlow FK, Shiels AL, Donovan CL. Body dissatisfaction in midlife women: The applicability of the tripartite influence model. Body Image. 2021;39:202–12.
15. Wiss D. Clinical Considerations of Ultra-processed Food Addiction Across Weight Classes: an Eating Disorder Treatment and Care Perspective. Curr Addict Reports. 2022;1–13.