What fasting REALLY does to you: Our top dietician reveals exact hour it turns on your body’s fat-burning switch, side-effects you need to power through… and meal plan to maximise weight loss and boost health

This week marks the beginning of Ramadan, a month of deep significance for Muslims around the world. Over the next month, worshipers will reflect on virtues such as spirituality, sacrifice, and patience, as well as fasting (not eating or drinking anything (including water) from dawn to sunset).

The spiritual benefits of this type of self-abstinence are of course at the forefront, but fasting in this way also has an effect on the body. Indeed, scientific evidence has shown that this type of intermittent fasting has health benefits, and there are steps that can help you transition into it.

The best way to describe the effect of intermittent fasting is to imagine the body as a hybrid car. When we eat as we normally do (eating large meals, snacks, drinks whenever we feel like it), we are running on readily available fuel. This fuel is primarily glucose derived from carbohydrates; Think of it like a car that uses gasoline.

However, when we fast, the body’s ‘gas tank’ (the liver and muscles where the tanks are kept) begins to run out.

When there is nothing left, usually after eight to 12 hours, the body goes into ‘electric mode’, drawing on the fat reserves we all carry. It’s as if the internal engine is revving up and saying ‘time to burn some of that stored energy’.

This metabolic shift to fat-burning mode is driven by several key processes.

Your blood sugar drops, you produce less insulin (the hormone that signals your body to store fat), and the liver starts producing ketones.

Ketones, derived from the breakdown of fat, are like a super-efficient fuel source for the brain and muscles. The body literally turns into a fat burning machine.

This transition is not always easy; The first few days of fasting can be quite scorching; You may feel extremely tired and possibly hungrier.

This is due in part to the initial drop in blood sugar and the body’s adaptation to using fat as its primary fuel source. Headaches may also occur due to dehydration.

If you are fasting during Ramadan, this month may also be a difficult month in terms of sleep; When you start intermittent fasting, some nights you will sleep soundly, and others you will toss and turn. This is linked to changes in hormones such as melatonin and cortisol, which regulate sleep-wake cycles and are affected by fasting.

Therefore, it is important to plan for fasting this month; You want to enjoy it in the healthiest way possible, and continuing unhealthy habits will make that even more challenging.

Think about foods that will keep you full and energized.

This means eating a balanced diet with protein, complex carbohydrates and healthy fats.

For sahur, the pre-dawn meal, this could mean foods like oats, nuts, and fruits consumed overnight. Avoid sugary foods right before the fast begins, otherwise you may experience dramatic blood sugar fluctuations and increased hunger.

Overeating at dinner can lead to digestive upset, especially if the meal contains high amounts of fat and processed carbohydrates; High-fat foods can slow digestion, causing an uncomfortable, overly full feeling; Processed carbohydrates, on the other hand, can also contribute to bloating and gas formation because they are quickly digested and fermented in the intestine.

Managing water intake is also very important.

From dusk to dawn, you should drink the same amount as on a non-fasting day. Also avoid coffee and tea; these are diuretics and may subsequently cause dehydration.

After about five days, the body should begin to adapt, which can ultimately lead to many health benefits.

A study last year in Indonesia examining the effect of Ramadan fasting on the weight and body composition of 137 healthy students aged 19 to 22 found that these students lost a significant amount of weight and body fat.

According to a 2023 study published in the European Journal of Clinical Investigation, fasting during Ramadan may also have a positive effect on the intestines; It can reduce bloating, pain, and heartburn.

It may also have a beneficial effect on lowering blood pressure, according to a 2021 study from the Journal of the American Heart Association. This is thought to be due to the nervous system being in a more relaxed state, known as parasympathetic tone, while fasting, but more research is needed.

There are also studies showing that fasting reduces inflammation.

In a 2018 research review published in the Journal of Nutrition and Intermediary Metabolism, researchers evaluated levels of cytokines (proteins that regulate inflammation in the body) in healthy adults before and after Ramadan.

Excessive levels of cytokines are linked to chronic inflammation, which can be associated with numerous health conditions, including cancer.

At the end of the study, participants’ cytokine levels were significantly reduced, which may have a short-term protective effect in healthy people (it’s worth noting that people with chronic health conditions are not expected to fast and the health effects may be different in other groups).

Emer Delaney is a dietitian based in London. He says there are studies showing that fasting reduces inflammation. Chronic inflammation may be linked to numerous health conditions, including cancer

It also has an impact on cognitive functions.

According to a 2016 study conducted by King Saud University in Saudi Arabia, people who fasted had a significantly improved ability to unconsciously shift their attention from one task to another.

Mental health symptoms may also improve.

In a review of 20 studies published last year in the Journal Discover Psychology: 72.7 percent, 66.6 percent, and 85.7 percent of studies reported reduced symptoms of depression, anxiety, and stress, respectively, and 71.4 percent noted improvements in psychological well-being.

This is likely due to the spiritual practice itself, the community connection, and the sense of accomplishment that comes with self-discipline.

This type of intermittent fasting has its drawbacks; People can become dehydrated, which poses a risk of gallstones.

And inevitably, after Ramadan, some will return to their normal lifestyle, which will lead to weight gain.

But by making the right nutritional choices, this time can also be an opportunity for change and a springboard to long-term benefits for body and mind.

Emer Delaney is a dietitian based in London.