Intermittent fasting might sound intimidating but it is probably something you have already done without intending. If you’ve ever skipped breakfast or gone a few extra hours between eating meals, these could both be considered types of an intermittent fast.

Taking up intermittent fasting as part of a healthy lifestyle means incorporating periods of fasting into your regular eating patterns on a daily or weekly basis. Studies suggest [1] that doing so could have significant health benefits, especially for people with type 2 diabetes. 

Leaving long gaps between eating isn’t something that will suit everyone. But intermittent fasting can be a simple and low-maintenance addition to a healthy lifestyle.

What is intermittent fasting?

You might have heard of intermittent fasting already as in recent years it has become a popular health trend. Intermittent fasting doesn’t define the type or amount of food you should eat. Instead, it defines time periods when you cannot eat, and other times when you can eat.  

As such, intermittent fasting is sometimes described as an eating pattern, rather than a diet.[1]

There are many different methods of intermittent fasting. One pattern involves not eating for 24 hours once or twice a week. For example, once a week you might stop eating after dinner on Monday, and not eat again until dinner on Tuesday. 

Another popular method is a daily 16-hour fast, which generally means skipping breakfast in the morning.

There are also different styles of fasting. During some fasts, you might eat nothing, or you might eat low-calorie meals or snacks. You can continue to drink water and other beverages like tea and coffee while you fast, but it’s generally advised to avoid adding sugar. 

What happens in your body when you fast?

The basic idea behind intermittent fasting is to encourage the body to make a metabolic switch. This happens as over time the body uses up its sugar stores from food eaten previously and starts to burn fat stored in the body instead. 

After food is eaten, it travels down to the gut where enzymes break it down and disperse the molecules into the bloodstream. We need insulin to get sugar from food into our cells to provide them with energy. Any extra sugar supplies that aren’t used up get stored in the form of fat. 

When no food is eaten for a long enough period, the body’s insulin levels go down as there is no sugar to transport into cells. When this happens, fat cells start to release their sugar for the body to use instead meaning that the body is burning fat.[2] 

How can intermittent fasting help with type 2 diabetes?

 Research into intermittent fasting is still in the early stages, and many studies have been carried out either on a small scale or on animals. However, they suggest that intermittent fasting could have significant health benefits.

People lost 3-8% of their body weight over 3-24 weeks of intermittent fasting

Barnosky et al, Transl Res

The most widely agreed-upon benefit is weight loss.[3] If you make intermittent fasting a part of your regular eating pattern, you’ll eat fewer meals and reduce your overall calorie intake. This can lead to significant weight loss, with one study finding that people lost 3-8% of their body weight over 3-24 weeks of intermittent fasting.[5]

For men especially, fasting can also cause a rise in blood levels of human growth hormone, which also promotes fat loss.[4]  

Weight loss is a positive for people with type 2 diabetes as it can help the body process insulin more effectively and prevent blood sugar spikes, contributing towards diabetes reversal.

Studies have also suggested that intermittent fasting makes people with type 2 diabetes less resistant to insulin in general, again helping the body to process sugar more effectively.[6] 

These are just a few of a wide range of general health benefits that could be linked to intermittent fasting, including improving life expectancy, heart and brain health, and reducing inflammation and the risk of cancer.[1]

While fasting, the body also initiates a process called autophagy, during which old or damaged cells in the body are destroyed. This can help reduce inflammation, prevent disease, and slow down the ageing process.[7]

Studies suggest that intermittent fasting makes people with type 2 diabetes less resistant to insulin

Rohner et al, Horm Metab Res

What are the mental benefits of intermittent fasting? 

Making a big change in your eating habits can sometimes be overwhelming, time-consuming, and even expensive. However, intermittent fasting can eliminate some of these stressful factors as you are simply cutting some meals from your routine.

You also do not have to completely change your existing diet to start or benefit from intermittent fasting.

While not everyone takes to intermittent fasting, it can offer a low-maintenance and simple method for losing weight and improving general health.

Are there any negative effects from intermittent fasting?

• The most obvious drawback is hunger. While your body is getting used to fasting it will still expect to eat at regular intervals and you may get hungry during your fast. As well as being uncomfortable, hunger can sometimes make us more likely to make poor diet choices at the end of a fast, such as compensating by eating large, carb-heavy meals. This can cancel out the potential health benefits of fasting.
• Fasting can cause light-headedness or problems concentrating at first. If you experience these feelings, you may wish to stop fasting. It is not advisable to fast during periods when you need to do a lot of physical activity or maintain a high level of concentration for your or others’ safety.
• For some people with type 2 diabetes, a dramatic change in eating routines can be risky. Intermittent fasting can cause blood sugars to drop too low (known as hypoglycemia), causing symptoms such as shakiness, nausea, blurred vision, and rapid heartbeat. If you are especially hungry after fasting, eating too much can also cause high blood sugar levels (known as hyperglycaemia), which increases the risk of diabetes complications.[8] In these cases, it is best to avoid fasting and stick to eating regular meals.
• Mealtimes are part of our routine and often break up the day by providing a moment to relax and socialise. Missing out on these moments may simply be difficult or unenjoyable for some people. 

 How can I start intermittent fasting safely?

Intermittent fasting aims to reduce calorie intake in a safe and controlled way, but it is still important to eat a healthy and sustaining diet. It's a good idea to talk to your doctor before you try intermittent fasting to discuss a balance of fasting and eating that will be healthy for you. Intermittent fasting is not recommended for children.

Workout a fasting plan that works with your schedule. For example, if fasting affects your concentration it might be harder to fast during a busy workday. Or, you might want to arrange your fast so that you don’t miss social moments, such as a shared family dinner. 

 It’s also a good idea to start intermittent fasting step-by-step to reduce symptoms like hunger and fatigue and build up your tolerance. For example, try eating your dinner at the same time every evening, then in the morning push your normal breakfast time back by one hour. When this feels comfortable, push it back by another hour and so on to gradually extend your overnight fast.

Make sure you drink plenty of water and other drinks when fasting. This will help keep up your energy levels and reduce the risk of light-headedness.

 If you feel too hungry or weak while you are fasting, it’s ok to break the fast and try again another time if you want to. Try to have some healthy snacks on hand.

Managing type 2 diabetes is all about managing blood sugar levels, and the food you eat is one of the most powerful tools you have available to help manage the condition. As well as controlling blood sugar levels, dietary changes can aid weight loss and we now know that with the right amount of weight loss for your body, it's possible to reverse type 2 diabetes.[9] The most important thing to do is to find a way of eating that suits you—for some, intermittent fasting might be enough, while others might benefit from a low-carb diet. Focus on how your body (and mind!) respond, how you feel, and if it's a way of eating that you can maintain. As with anything related to dietary changes, do speak to your doctor before making major adjustments to how you eat—particularly if you have type 2 diabetes.