Fasting is a practice that involves abstaining from food for a certain period of time, and has been used for various purposes such as weight loss, religious observance, and overall health improvement. When you fast, your body goes through a series of changes as it adjusts to using alternative sources of energy. Here’s a detailed look at what happens to your body when you fast for different periods of time:
After 8 hours of fasting, your body has used up all the available glucose in your bloodstream and begins to break down stored glycogen (a type of carbohydrate stored in the liver and muscles) into glucose to fuel the body. The liver also starts producing ketones, which are an alternative source of energy that can be used by the brain and other organs.
After 16 hours of fasting, your body has used up all stored glycogen and starts breaking down fat into molecules called fatty acids, which can be used as an energy source. This process, known as lipolysis, continues as long as you remain in a fasted state. Also at this time autophagy can begin. Self eating, or cellular recycling.
After 24 hours of fasting, your body has depleted its stored glycogen and is relying almost entirely on fat for energy. You may feel hungry, irritable, or low on energy at this point, but your body will also be releasing human growth hormone (HGH), which helps preserve muscle mass and promotes fat loss.
After 48 hours of fasting, your body is fully adapted to using fat as its primary energy source. You may still feel hungry and experience some energy fluctuations, but your body is more efficient at using fat for fuel. You may also start to notice some of the potential health benefits of fasting, such as improved insulin sensitivity and reduced inflammation. Your autophagy will also deepen and become more powerful.
After 72 hours of fasting, your body is in a state of ketosis, where it primarily uses ketones for energy. You may continue to feel hungry and have energy fluctuations, but your body can function normally on ketones. At this point, you may also see more noticeable improvements in body composition and other health markers. At this time you will be in full autophagy.
It’s important to keep in mind that everyone’s body responds differently to fasting, and the above timeline is just a general guide. It’s also crucial to consult with a healthcare professional before starting a fasting regimen, as it may not be suitable for everyone.