Intermittent Fasting: Helpful or Hindering Optimal Diabetes Control?

Intermittent fasting (IF) is an eating pattern requiring individuals to cycle between periods of eating and fasting (consuming no food or foods with very low kilojoules). Unlike traditional diets which focus on overall kilojoule intake, IF outlines specific times to eat. 

There are a variety of ways people can achieve IF:

Alternate day fasting- Days of fasting are separated by days of unrestricted eating, 

Periodic fastingIndividuals fast for one or two days of the week, like the 5:2 and 6:1 diets

Time-restricted feeding: This is the most popular method of IF and allows people to eat within a specific time frame throughout the day. An example is the 168 method whereby food consumption is allowed over an 8 hour period and the remaining 16 hours of the day are fasting. 

The idea behind IF is simple — reduce the amount of hours a person eats to create a kilojoule deficit and therefore weight loss will occur. In addition, short periods of fasting encourage the body to use stored fat and glucose (in the form of glycogen) for energy, further resulting in weight loss.

Since we know weight loss can help improve blood glucose and cholesterol levels and over 90% of people with type two diabetes are overweight, IF may have a place in achieving positive outcomes. (Bramante, Lee & Gudzune, 2017). However, it is important we look at the scientific evidence surrounding IF as we know correlation is not causation. 

The current scientific evidence 

A recent literature review (a research paper combining the results of multiple studies) explored whether IF should be considered as a dietary treatment for people with type two diabetes (Albosta & Bakke, 2021). The researchers examined either alternate day fasting, periodic fasting or time-restricted feeding to determine any improvements with insulin sensitivity. 

Before we discuss the findings of the literature review, here is a quick refresher on the underlying cause of diabetes so you can better understand the impact of IF. Insulin resistance occurs when muscle, fat and liver cells cannot respond to insulin appropriately. This prevents glucose from entering cells and instead accumulates in the bloodstream. An excessive amount of leptin (a pro-inflammatory hormone) increases inflammation throughout the body and this also contributes to diabetes. 

This review found that IF is effective in improving body weight, fasting glucose and insulin test results, insulin resistance and levels of leptin and adiponectin (an anti-inflammatory hormone that enhances cells response to insulin) (Albosta & Bakke, 2021). Improvements observed with leptin and adiponectin levels were associated with better appetite control and decreased levels of chronic inflammation. Ultimately, the literature review concluded that IF is an effective dietary treatment for people with type two diabetes (Albosta & Bakke, 2021). 

However, a number of the studies included in the review were flawed. Firstly, many of the randomised controlled trials failed to include participants diagnosed with diabetes. Secondly, the study durations were less than a year so we do not know the long- term impact of IF and thirdly, the impact of IF independent of weight loss remains unclear. Hence, further research is required to address the impact and safety of IF longer term, and separate the effects of IF and weight loss for people with diabetes. 

Do you want to try IF?

Please speak with your doctor or dietitian before starting IF to ensure it is a safe short and long-term option for you and for individualised support. 

IF is not appropriate for everyone and is unsafe for people who are

  • Prescribed certain medications like sulphonylureas, insulins and / or glinides and for people with type one diabetes as IF can significantly increase the risk of hypoglycaemia.
  • Experience frequent hypoglycaemia
  • Elderly
  • Pregnant or lactating
  • Immunodeficient
  • Experiencing eating disorders or in remission


Tips for starting a safer IF régime 

  1. Begin with smaller fasts and build up over time under the supervision of your doctor and dietitian. A 12 hour overnight fast (8pm to 8am) is generally a good place to start. 
  2. Stay hydrated. Good hydration is paramount to good health and water is permitted during fasts. Try herbal tea to curb sweet cravings during a fast. 
  3. Break your fast gently to allow your digestive system to fully process food and avoid stomach-aches. This will also prevent overeating.
  4. Plan your meals. Have nutritious food prepared to eat when you come out of your fast to avoid binging on unhealthier foods.
  5. Maintain balanced meals. Ensure each meal contains a good source of protein, fibre, healthy fats, and low glycaemic index carbohydrates like milk, beans and wholemeal pasta.. This will help you feel full and satisfied. 
  6. Listen to your body. If you are experiencing dizziness, headaches, nausea or extreme hunger, it is okay to break your fast. Speak with your doctor if symptoms persist. 
  7. Try to exercise during your eating window. If your muscles are inadequately fuelled, you are at greater risk of injury or hypoglycaemia. 

Remember to speak with your doctor or dietitian before starting IF to ensure it is safe and appropriate for you. For further personalised information about IF and how it may support you to lose weight and manage your BGLs, book an appointment with Rebecca

Co-authored by student dietitian, Charlotte Manning 

Reviewed by dietitian, Rebecca Greco 


Albosta, M., & Bakke, J. (2021). Intermittent fasting: is there a role in the treatment of diabetes? A review of the literature and guide for primary care physicians. Clinical Diabetes and Endocrinology, 7(3), 1 – 12. doi 10.1186/s40842-020 – 001161

Anton, S. D., Moehl, K., Donahoo, W. T., Marosi, K., Lee, S. A., Mainous, A. G., Leeuwenburgh, C., & Mattson, M. P. (2018). Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity (Silver Spring, Md.), 26(2), 254 – 268. doi 10.1002/oby.22065

Bramante, C. T., Lee, C. J., & Gudzune, K. A. (2017). Treatment of Obesity in Patients with Diabetes. Diabetes Spectrum, 30(4), 237 – 243. doi 10.2337/ds17-0030

Dia​betes​.co​.UK. (2019). 5:2 Fasting Diet. Retrieved from https://​www​.dia​betes​.co​.uk/die…,on%20blood%20sugar%2Dlowering%20medications%20.

Grajower, M.M., & Horne, B. D. (2019). Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients, 11(4), 873. doi 10.3390/nu11040873.

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