What is intermittent fasting, its benefits, and the science behind it

Authored by

Dr Adam Williams

23 August 2022

What is Intermittent Fasting?

Intermittent Fasting (IF) is the practice of eating meals between cycles of fasting. The basis of IF is that by limiting your calorie intake, your body goes into a calorie deficit, which means it has fewer calories to maintain its current weight. The body then uses up its fat stores for energy, leading to weight loss. It’s about when you should eat rather than what you should eat. Although, when you do eat, you should aim for a nutritious balance of foods. This is one of the many methods that can be used to lose weight. Wellness professionals have different opinions about the best method; however, any positive change involving eating and when can be beneficial.

Fasting History Around The World

There are examples of IF throughout cultural backgrounds, such as during religious practices, including the Great Lent for Christians, the holy month of Ramadan for Muslims, Yom Kippur for those practising Judaism, and Zhaijie for Chinese Buddhists.

Methods of Intermittent Fasting:

There are many methods to undertake Intermittent Fasting; a medically reviewed article on healthline.com by Nutrition PhD holder Grant Tinsley suggests some of the more popular methods. Each fasting method comes with its change in habits and potential for results, but is it worth it? MedialNewsToday cites PubMed Central as finding that research has shown that fasting for 10-16 hours can lead the body to turn its fat into energy and promote weight loss. If you are new to fasting and love to eat, then an easier way to start would be to set your fasting period over your sleeping schedule.

For any beginner, the easiest way to do this would be to start with the time-restricted method and you could always switch to one of the more demanding methods listed in the order below. These more intense fasting methods can include fasting for extended periods and may include a continuous calorie restriction. You will learn to understand your body's needs during a fasting period and can tailor your plan to your lifestyle.

Be mindful that losing weight often requires an all-inclusive approach, combining calorie control, active and wholesome lifestyle practices, and sometimes, when suitable, the use of medical support with products like Wegovy.

Time-restricted eating

Time-restricted eating – a popular example of this method is known as the 16/8 method, whereby you fast for 16 hours per day while eating two or more meals during the remaining 8-hour window.

The 5:2 diet – For some, an easier approach may be the 5:2, where you would eat as you already do for five days a week, and the only change would be to limit your intake of calories to 500-600 for each of the remaining two days. When restricting calories, it's important to still ensure that you have analysed the health benefits and are not moving too fast, especially if you have underlying medical conditions or health concerns.
Eat Stop Eat –A more extreme version of the 5:2 method would be Eat Stop Eat. When you fast for 24 hours once or twice per week.
Alternate-day fasting – As straightforward as the name suggests, you would fast every other day, rather than every day or a set number of days per week.

When considering a new routine that involves eating at different times, it's important to research how to reduce your calorie intake slowly and when to schedule your eating window so you can manage your new diet's side effects.

Does it work?

Studies by PubMed Central have shown that various ways of undertaking intermittent fasting give various results. For example, mice undertaking fasting by limiting their eating periods to an 8-hour window led to decreased chances of obesity, inflammation and diabetes compared to mice that did not fast. Mice aside, their studies showed that from a sample of 107 overweight women, when they undertook the 5:2 method of IF, they also showed signs of weight loss.

Should you do it?

Healthline.com has taken PubMed Central’s studies and weighed up some of the pros and cons of undergoing IF. The change in eating patterns brought about by methods such as the Time-restricted method and the 5:2 method has been directly linked to weight loss and improved metabolic health. This means your health could benefit from lowered blood pressure and even protecting brain health. However, there will always be side effects to such a significant change in your eating habit, and one should not be surprised if you feel hungry or become moody. More serious side effects include fatigue, headaches, and even constipation.

Who Should Avoid Intermittent Fasting

All things considered, it is always important to look at the pros alongside the cons. It may work, but it may not be for everyone either.

Intermittent fasting has not been recommended for some groups; these include:

Those who have previously or currently have any eating disorders,
Children,
Those with certain medical conditions,
People with chronic diseases,
People who are pregnant or breastfeeding.

Final Words

If you choose to try IF, it is always important to keep a healthy diet of the foods you eat outside of fasting times.

It is also important to remember to combine a new diet with exercise. If your goal is for fat loss, the most effective way to meet your goal is to include a variety of healthy lifestyle choices in your day-to-day.

While research shows that IF has benefits, intermittent fasting may not be suitable for you or your specific lifestyle. Adding a new dietary plan that involves fasting can be intimidating, so if you wish to learn more, speak to a dietician or healthcare professional.

At Welzo, we offer a large range of nutritional and lifestyle advice, treatments and tests. To see our nutrition hub, click here.