Can Fasting for 24hrs Really “Reset” Your Metabolism?

The answer is, yes. Yes, it can.

Fasting itself is nothing new, it’s an old custom that can be found all over the world. Fasting is even noted in our everyday language in the word breakfast, which is a combination of the words “breaking the fast.” For many cultures, religions, and philosophies, fasting is common practice. This includes Christianity (especially Catholicism but also many others), Islam, Buddhism, Judaism, Taoism, and Hinduism, just to name a few. Even modern celebrities such as Beyonce, Ben Affleck, and Hugh Jackman swear by some form of fasting. All of these people have different methods of fasting, which can last for anywhere from a couple of hours to a few days. Their reasons for fasting may be for religious or spiritual purposes, psychological or physical health, or in the case of the Geneva canton in Switzerland – leftover practices from the Middle Ages that have just stuck around (fasting was used as a penitence for the population after a war, the plague, or other catastrophic happenings. Geneva now has an annual public holiday for fasting).

So, if anyone was wondering if it’s a safe thing to do, they can rest assured that it is. People are doing it all the time, all over the planet. Truthfully, the majority of people fasting are doing it for self-cleansing or spiritual purposes, and not specifically for their physical health. But whether they’re aware of it or not, they are also reaping a whole lot of physiological health benefits in the process.

Here are just a few of the biological processes that happen in your body when you engage in cycles of prolonged periods of fasting:

• A reduction of your white blood cells, leading to stronger immune system protection
• The encouragement of the metabolic process called ketosis, or the fat-burning state, which helps you burn through your fat reserves
• The improvement of insulin sensitivity, lowering your chance of insulin resistance
• Benefits to your cardiovascular health, including a better blood composition and lowering of blood pressure
• Promotion of higher satiety, or a sense of fullness when eating (in turn helping to maintain a healthy weight)
• Decrease of oxidative stress, by giving your metabolizing process a break (simply metabolizing foods constantly can create free radicals)
• Promotion of the secretion of the human growth hormone
• Inhibits the production of inflammatory proteins like cytokines, which can lead to premature aging
• Lowering of cholesterol levels, also helping maintain heart health and prevent heart disease
• Increase of your chances of longevity by slowing the aging process (an example for this is that when your body is denied food, it’s biological processes become more economical in the hope of prolonging life)

A large part of the reason for many of these advantages to health is that periods of fasting kill off older immune cells that may be damaged, old, or malfunctioning, and help generate new healthier immune cells. This is a process known as autophagy. During autophagy, your body feels it is in a state of starvation, and so it begins to ‘recycle’ cells. Malfunctioning cells are destroyed, and healthy cells that respond well to famine or other stressors are promoted and maintained.

Many of the benefits noted in this list are part of the answer to the question “can fasting reset your metabolism”. The simplified version of the answer to this question is that when your body reaches the fat-burning state of ketosis (which is literally a state of starvation, but in this case, only for 24 – 48hrs), your metabolism does indeed change. Instead of reaching for the sugars or glycogen that it normally needs to burn for fuel, your body will start to burn its fat reserves. In a single 24hr period of not eating, your body’s metabolism will shift as it rushes to adjust to this new state.

The more in-depth explanation is that normally when someone eats, the carbohydrates they are eating are broken down into glycogen or glucose. Glucose is then used as the main source of energy for the various functions of the body. When ketosis (the fat-burning state) occurs from fasting, intermittent fasting or as a result of a ketogenic diet, the body breaks down fats into ketones and sources its energy from these ketones instead of the usual glucose.

Occasionally cycling through prolonged periods of fasting (for example, one or two days a month) will have a positive impact on your metabolism, body, and brain. It may feel a little lonely, and let’s not mess around, it is going to take a lot of willpower the first few times you incorporate fasting into your lifestyle. But whether you are a runner, an athlete or just someone interested in healthy body composition, it is definitely worth it to skip just a few meals every month. It’s definitely helpful if you can get a friend to join you and support each other.  And there is one fun aspect to it – nothing will taste better than your first meal breaking the fast!