Type 2 diabetes mellitus is becoming increasingly prevalent globally with many developed countries seeing a rise in the diseased population.  Complications with diabetes are primarily due to metabolic impairments (such as insulin resistance), which are often compounded due to excessive weight and the presence of other cardiovascular diseases or risk factors.
The cornerstones of diabetes management are weight loss, diet, exercise, and taking anti-diabetes medications regularly. Despite this, strict glycemic control becomes difficult, which warrants alternative measures.
Intermittent fasting can potentially fill the gap. This is a form of controlled fasting that involves not consuming any calories for a certain period of time every day. Studies have shown that it could potentially be very beneficial for people with diabetes. [1-4] But remember everybody is different, so choose a diet that best suits you and your health needs.
Types of intermittent fasting
The basic principle of intermittent fasting is to avoid eating for an extended period, instead of consuming water and plain coffee or tea (without milk, sugar, or any other additives) during that time. Listed below are the protocols that have been used in recent scientific studies [1-3].
- The 16:8 or 18:6 fast: Here, you consume all your meals in an 8-hour or 6-hour window, and eat nothing for the remaining 16 or 18 hours.
- The 24-hour fast: Here, you eat just one meal a day, and avoid any caloric intake in the remaining hours.
- The 5:2 diet: In this protocol, you eat as usual for five days of the week, and then consume only 500 calories in the remaining two days.
After 12 hours of no food, the stored glucose (as glycogen) in the liver is used up; thus, insulin levels also go down. The body then switches to using fat for energy. Fat breakdown releases fatty acids, which are used by the body instead of glucose as fuel.
Studies suggest that short-term Intermittent fasting may have benefits for the body .
- Increased insulin sensitivity – low insulin levels in the body helps with reducing insulin resistance and hence increasing the body’s sensitivity to insulin.
- Decreased fatty tissue – this is partly due to the use of fat for fuel and partly due to low insulin, which prevents fat build-up.
- Weight loss – decreased fatty tissue leads to weight loss, which can vary from approximately 1 kg per week to a steady loss of 14 kg over six to seven months. [1, 3]
- Improved blood sugar control – intermittent fasting can lead to better fasting and postprandial blood sugar levels, reduced HbA1c levels, and decreased hyperglycemia immediately after food. 
- Better artery health – the low-insulin state of fasting prevents the increase in the levels of compounds that eventually cause arteries to harden.
- Potentially reduced cardiovascular complications – this is a result of the benefits mentioned above. However, long-term studies are needed to confirm this.
– Though these studies show great benefit to the health of diabetics in general, these studies were conducted on small sample groups and a lot more research is needed in this regard to help generalise these effects.
The risks and precautions
Modern humans are not used to intermittent fasting. So, food restriction and/or inadequate water intake can cause some short-term problems, especially in people with diabetes. 
- Hypoglycaemia – The most immediate risk for people with diabetes practising intermittent fasting is hypoglycaemia or low blood sugar, especially for those taking insulin or sulfonylureas. With precautions, however, hypoglycaemic events can be as low as once a month.  People interested in intermittent fasting should learn about the symptoms of and precautions related to hypoglycaemia, and undergo fasting only after consulting with their doctor.
- Nutrition deficiencies – if the food consumed in the non-fasting times is not healthy and balanced, then protein, vitamin, or mineral deficiencies may occur. This can be remedied by taking appropriate portions of macro and micronutrients as meals or supplements.
- Dehydration – people who do not drink much water can suffer from dehydration during the fasting periods. Adequate intake of water and plain tea (black, green, and herbal) is a must.
- Other issues due to lack of food/water intake – Lack of food or water can cause problems such as dizziness, hunger pangs, insomnia, and weakness, at least in the beginning, especially in people with metabolic diseases such as diabetes. This depends on the individual’s health and usually disappears once you get used to the fasting regimen.
- At-risk populations – some people are especially sensitive to these risks and should not undergo intermittent fasting, e.g., pregnant and lactating women, children, and very old adults.
Overall, the benefits seem to outweigh the risks, which reduce in time with better management of fasting schedules and meals. The benefits also differ on what kind of fasting regimen is used: stricter fasts (e.g., 18:6 or one meal a day) will provide more benefits, but they can be harder to maintain and may require more careful monitoring of blood sugar level and water intake.
Before starting any intermittent fasting regimen, it is imperative that you consult your doctor. You may need to pay attention to your medicines (reducing the dose or changing the schedule/medication), monitor your glucose, and maintain fluid intake.
Summary and conclusions
Some studies show that intermittent fasting has many benefits, especially for people with diabetes. These include weight (fat) loss, increased insulin sensitivity, and other metabolic and cardiovascular benefits (e.g., promotion of cellular autophagy). While the findings are promising, larger studies are needed to confirm them.
Meanwhile, try to eat a healthy low-carb diet for a week before you begin your fasting. Remember to consult your doctor at every stage.
- Furmli S, Elmasry R, Ramos M, Fung J. Therapeutic use of intermittent fasting for people with type 2 diabetes as an alternative to insulin. Case Reports. 2018 Sep 18;2018:bcr-2017.
- Corley BT, Carroll RW, Hall RM, Weatherall M, Parry‐Strong A, Krebs JD. Intermittent fasting in Type 2 diabetes mellitus and the risk of hypoglycaemia: a randomized controlled trial. Diabetic Medicine. 2018 May;35(5):588-94.
- Arnason TG, Bowen MW, Mansell KD. Effects of intermittent fasting on health markers in those with type 2 diabetes: A pilot study. World journal of diabetes. 2017 Apr 15;8(4):154.
- Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019 Apr;11(4):873.