Should You Try Intermittent Fasting? A Dietitian Explains Who It Is and Isn't For

By Tom Price, Accredited Practising Dietitian

Disclaimer: This article provides general information only and is not intended for personalised dietetic advice nor suitable for individuals with a current or past eating disorder. If you have concerns about disordered eating, please seek support from an eating‑disorder‑informed healthcare team.

Introduction

Little debate exists around the fact that food and nutrition is a polarising space. Within this space, few topics receive as much attention as fasting (AKA intermittent fasting), both on social media and in our consultation rooms. This is largely due to circulating information about its potential benefits in reducing the risk and supporting the management of metabolic diseases such as diabetes, cardiovascular disease, and even Alzheimer’s disease.

While the answer to the question, “Is this for me?” is highly individual, this article will explore some of the nuances around when fasting may, and may not, be appropriate.

What is fasting?

Fasting refers to the bodily state in which the digestive process of breaking down and absorbing food has finished. Rather than actively processing incoming nutrients, the body is utilising stored energy to support functions such as brain activity, muscle contraction, and countless other processes. In contrast, the fed state is the state of actively digesting and absorbing food.

Intermittent fasting, or fasting, is an umbrella term used to describe a variety of methods that increase the time spent in the fasting state.

Generally speaking, there are three main ways people engage in fasting:

• Time Restricted Eating (TRE, TRF, 16/8) - where the eating window is shortened to around 8 hours (e.g. 12 noon - 8 pm).

• 5:2 method - where calorie intake is reduced to approximately 25% of baseline requirements on two non-consecutive days per week.

• Alternate Day Fasting (ADF) - which alternates between days of consuming around 125% of energy requirements and days of approximately 25% of energy requirements.

In some instances, these guidelines can be tailored to the individual. For example, with TRE the fasting window can be moved to suit lifestyle demands and can even be lengthened or shortened by several hours. While this flexibility may be useful for some individuals, there are times when fasting comes with risks, or may be inappropriate altogether. Let’s explore the potential benefits first.

What are the benefits?

Broadly speaking, there are two scenarios, which often coexist, where introducing a personalised fasting regimen may be useful.

The first is for those who struggle with eating structure. In this context, TRF can act as guardrails, helping define when to start and when to stop eating for the day, which may be a challenge for many people including those with challenges in executive function, routine and/or sensory needs. This can be taken a step further by also deciding where each meal will be eaten, a concept coined “pinned eating” by Ogden and colleagues (2020). Deciding when and where one will eat fosters predictability and encourages planning the contents of each meal, which can be helpful for many people, regardless of their goals (Ogden et al., 2020). 

The second scenario is managing total calorie intake for people in higher-weight bodies who are interested in weight-focussed approaches to improve biomarkers such as high blood pressure, elevated blood sugar, high cholesterol, and Metabolically Associated Fatty Liver Disease (MAFLD). Improvements in blood sugar, cholesterol, and triglycerides are often seen, predominantly due to reductions in visceral fat around the organs (Gu et al., 2022). However, research suggests fasting is generally no more effective than other forms of calorie restriction (Pascual et al., 2022). Further, improving healthy behaviours, even without weight loss, can still result in meaningful health improvements (Sutton et al., 2018 and Meir et a., 2025). Regardless, fasting can work well for some individuals depending on various factors assessed during an initial dietitian consultation.

In summary, when executed well and used in appropriate circumstances, intermittent fasting can improve chronic disease markers, with some forms of fasting potentially facilitating structured eating. However, there are real risks involved that must be considered, too.

When is it a risk?

By definition, fasting focuses on food restriction and involves extending the time spent without eating. For some individuals, this can have negative implications that far outweigh the potential benefits.

From a hunger and fullness perspective, fasting often requires ignoring internal cues that are critical for fuelling the body appropriately. Suppressing hunger may lead to later compensation, often in the form of excessive intake and less nutritious choices. Over time, this pattern may contribute to chronic disease, disordered eating, and eating disorders such as anorexia nervosa, bulimia nervosa, binge eating disorder, among others. It may also exacerbate issues in recognising hunger and fullness signals for people living with neurodivergence such as autism and ADHD.

There is a growing body of evidence indicating that intermittent fasting can exacerbate or contribute to eating disorders, particularly among adolescents and young adults, individuals with body dissatisfaction, a history of dieting, overweight status, or orthorexic tendencies (Ganson et al., 2022; Augimeri et al., 2025; Domaszewski et al., 2024). Repeated denial of hunger cues may reinforce disordered eating behaviours and cognitions, including cycles of restriction and bingeing. Furthermore, fasting can promote rigid food rules and beliefs about calorie intake due to its structured time and quantity cut-offs. For these reasons, individuals experiencing disordered eating or an eating disorder should consider alternative strategies under the guidance of a healthcare professional.

Another situation requiring caution is when taking certain medications, particularly blood pressure lowering medications and some diabetes medications. Extended periods without food, combined with these medications, can cause blood pressure or blood sugar to drop to unsafe levels, posing significant risk, including death. While fasting itself may be safe in some contexts, and water intake is generally encouraged, the interaction between meal timing, meal composition, and medication requires careful medical supervision.

Perhaps less immediately dangerous but still life altering is the potential risk of gut dysfunction. Eating less regularly and compensating later with large, rapid meals can disrupt digestive function, leading to symptoms such as reflux, bloating, abdominal discomfort, and irregular bowel movements. While these symptoms are influenced by many factors, including stress, physical activity, eating disorders, medications, allergies, and intolerances, irregular eating patterns are a common contributor.

In a world filled with stress and distraction, many of us have already lost touch with our internal hunger and fullness cues. Likewise for those with neurodivergence who may not reliably feel hunger cues. For some, fasting may exacerbate this disconnection, leading to the issues described above. For others, however, it may serve as a practical lever to help achieve a goal set collaboratively with their healthcare team.

Finally, regarding claims about reduced neurological disease risk and lifespan extension, much of the evidence relies on animal studies, with limited robust human data to support these outcomes (Mattson et al., 2017; Kubicka et al., 2025). In contrast, we have far stronger and higher quality evidence showing that consuming regular, balanced meals aligned with dietary patterns such as the Mediterranean Diet is associated with improved longevity, brain health, and metabolic outcomes (Martina-Gonzalez & Martin-Calvo, 2016).

Conclusion

Like many circulating nutrition claims, intermittent fasting may be hyped beyond its true capabilities. While it can be a viable treatment option for some individuals living with chronic diseases such as diabetes or cardiovascular risk factors, it also carries meaningful risks. These range from gastrointestinal disturbances to the promotion of disordered eating and eating disorders, conditions that are serious and require substantial medical care. Particular attention is also warranted with neurodivergent individuals as fasting may help or hinder progress, depending on strategies chosen and patterns of thinking.

If fasting is something you are considering, discussing your individual circumstances with one of our dietitians is the safest way to determine whether it aligns with your health goals and medical needs.

References

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Domaszewski P, Rogowska AM, Żylak K. Examining Associations Between Fasting Behavior, Orthorexia Nervosa, and Eating Disorders. Nutrients. 2024; 16(24):4275. https://doi.org/10.3390/nu16244275 

Elortegui Pascual P, Rolands MR, Eldridge AL, et al. A meta-analysis comparing the effectiveness of alternate day fasting, the 5:2 diet, and time-restricted eating for weight loss. Obesity (Silver Spring). 2023; 31(Suppl. 1): 9-21. doi:10.1002/oby.23568  

Ganson KT, Cuccolo K, Hallward L, Nagata JM. Intermittent fasting: Describing engagement and associations with eating disorder behaviors and psychopathology among Canadian adolescents and young adults. Eat Behav. 2022;47:101681. doi:10.1016/j.eatbeh.2022.101681

Gu L, Fu R, Hong J, Ni H, Yu K, Lou H. Effects of Intermittent Fasting in Human Compared to a Non-intervention Diet and Caloric Restriction: A Meta-Analysis of Randomized Controlled Trials. Front Nutr. 2022;9:871682. Published 2022 May 2. doi:10.3389/fnut.2022.871682  

Kubicka J, Grabowska M, Grabowska K, Wiśniewska A, Dąbek J, Kosucka W, Kaszyńsk, K. Intermittent Fasting and Its Health Implications: A Systematic Review of Existing Research (2025).. Quality in Sport, 40, 59420. https://doi.org/10.12775/QS.2025.40.59420 

Mattson MP, Longo VD, Harvie M. Impact of intermittent fasting on health and disease processes. Ageing Res Rev. 2017;39:46-58. doi:10.1016/j.arr.2016.10.005 

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Ogden J, Pavlova E, Fouracre H, Lammyman F. The impact of intuitive eating v. pinned eating on behavioural markers: a preliminary investigation. J Nutr Sci. 2020;9:e34. Published 2020 Aug 12. doi:10.1017/jns.2020.25  

Sutton, E., Beyl, R., Early, K., Cefalu, W., Ravussin, E., & Peterson, C. (2018). Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes.. Cell metabolism, 27 6, 1212-1221.e3 . https://doi.org/10.1016/j.cmet.2018.04.010.