Fasting or abstinence from food for specific periods of time is not a new concept. From health reasons to religious sacrifice, the concept of fasting has long been a part of our consumption ecosystem. It is also important to remember that fasting has been a practice throughout human evolution. Our hunter-gatherer ancestors certainly did not have regular and convenient access to food via the supermarkets we have today. Nor did they have refrigerators to keep food fresh. If they couldn’t find a source of food that day, they didn’t eat! It is probably fair to say that the human body is able to function without food for extended periods of time.

Nowadays, people may fast for a myriad of reasons. However, the process and methodologies of fasting may differ.

It is probably fair to say that most people in our modern-day and age fast in order to detox and/or to lose weight. However, fasting over long periods of time can be very dangerous, especially if you are not properly supervised or guided by a trained medical professional or nutritionist.

If you start fasting blindly, you will lose weight over a period of time. However, you may end up depleting all the glycogen in your liver which leads to your body reverting to another energy source in order for it to operate. This will most often be your body’s source of fat or protein. This could lead to the breakdown of important muscles including your heart which can result in heart failure. Long periods without eating will also decrease an individual’s energy levels and without receiving proper nutrition, you run the risk of infection and illness due to a weakened immune system.

This is where the concept of intermittent fasting (IF) has found a loyal group of followers. IF is an eating pattern that cycles between periods of fasting and eating. In other words, it does not dictate that you abstain from food for days at a time but rather, it commonly regulates the periods of time in a day where you can eat. It also does not specify which foods you should eat but rather when you should eat them. It is therefore not a diet in the conventional sense but more accurately described as an eating pattern.

Common IF methods involve daily 16-hour fasts or fasting for 24 hours, twice per week.

There are several different ways of doing IF. During the fasting periods, you eat either very little or nothing at all.

These are the most popular methods:

• The 16/8 method: This involves skipping breakfast and restricting your daily eating period to 8 hours, such as 1–9 p.m. Then you fast for 16 hours in between.
• Eat-Stop-Eat: This involves fasting for 24 hours, once or twice a week, for example by not eating from dinner one day until dinner the next day.
• The 5:2 diet: here, you consume only 500–600 calories on two nonconsecutive days of the week, but eat normally the other 5 days.

By reducing your calorie intake, all of these methods should cause weight loss as long as you don’t compensate by eating much more during the eating periods. Many people find the 16/8 method to be the simplest, most sustainable and easiest to stick to. It’s also the most popular. Unsurprising, given that it includes your sleep time which makes it easier to stick to.

When you fast, several things happen in your body on the cellular and molecular level. For one, your body adjusts hormone levels to make stored body fat more accessible. Your cells also initiate important repair processes and change the expression of genes.

In addition to lowering insulin and increasing growth hormone levels, it increases the release of the fat-burning hormone norepinephrine (noradrenaline). These hormone changes may enhance your metabolic rate by 3.6–14%.

Helping you eat fewer and burn more calories IF causes weight loss by changing both sides of the calorie equation. In short, IF can lead to better cell function, longevity and weight loss.

Some who advocate IF have suggested that the practice of IF harnesses the benefits of fasting without causing the muscle loss that the continuous restriction of calories could cause. Some studies have also indicated that IF can have many benefits for your body and brain. It can cause weight loss and may reduce your risk of type 2 diabetes, heart disease and cancer. It may also help you live longer.

While IF is popular with fitness enthusiasts, it is important to note that research is ongoing on IF and it is recommended that people speak to medical professionals before embarking on this.

If you are underweight or have a history of eating disorders, IF may not be the most suitable option for you.