Fasting means choosing not to eat food for a period of time each day. You might not eat for several hours or only have one meal a day. Not eating for certain periods can help raise ketone levels. Ketones are chemicals your liver makes that your body uses as energy. But that's not all fasting does. It also offers health and mental benefits you might not expect.
How Fasting Works
The liver's ketone-making process looks something like this: Glucose (sugar) is the main fuel your cells use to produce energy. Fasting uses the liver’s store of glucose, causing cells to release fats. When these fats travel to your liver, they’re converted to ketones your body uses for energy.
Before humans learned how to farm, people hunted and gathered food to survive. They would go long stretches without eating. It took a lot of energy and time to gather nuts and berries or hunt game. The human body adapted to that by using what stores of energy it had. Today you don’t have to hunt and gather your food the way your ancestors did, but fasting may still benefit your physical and mental well-being.
With intermittent fasting, you can eat only during a specific time. When you go hours without food, the body uses all its sugar stores and starts burning fat. This is a phenomenon known as metabolic switching. As your body burns through the calories consumed during your last meal, intermittent fasting prolongs that period and then begins burning fat.
During the times you’re not eating, you can drink water and zero-calorie beverages such as black coffee and tea. And during your eating periods, you can “eat normally,” but that doesn't mean eating whatever you want. It’s recommended to stay away from high-calorie junk food, fried food, and treats.
The most common fasting plans include:
16/8 fasting. This is the most common approach. It involves eating every day within an eight-hour window and then fasting for 16 hours after your last meal.
5:2 approach. This approach involves regularly eating five days a week. For the remaining two days, you limit yourself to a single 500–600 calorie meal.
Longer periods without food, such as 24-, 36-, 48-, and 72-hour fasting periods, may be dangerous. If you go too long without eating, it might encourage your body to store more fat in response to starvation. If you want to fast the right way, learn about the best methods and test them.
Benefits of Fasting
Mental function. When you fast, your body has less toxic materials flowing through the blood and lymphatic system, making it easier for you to think. While fasting, the energy you’d normally use to digest food is available to be used by the brain.
You likely won’t notice this mental change until the first few days of a fast because your body takes time to adjust. You might have headaches or pain points at the beginning of the process. But after your body clears itself of toxins, your brain has access to a cleaner bloodstream, resulting in clearer thoughts, better memory, and increased sharpness of your other senses.
Healing rejuvenation. Fasting puts your body through a rejuvenation experience. It dissolves diseased cells, leaving only healthy tissue. There's also a noticeable redistribution of nutrients in the body. The body hangs onto precious vitamins and minerals while processing and getting rid of old tissue, toxins, or undesirable materials.
Increased willpower. Choosing to fast requires mental strength and the ability to resist short-term gratification to pursue long-term goals. When you choose to participate in such a challenging exercise and succeed, you’ll likely experience enormous gratification and a renewed sense of accomplishment.
Tips to Use Fasting to Improve Your Well-Being
Ease into it. Try not to go from eating to not eating all at once. Instead, try to cut back on food and drink intake over a few days or weeks.
Avoid sugar. Food and cookies made from sugar can make you feel satisfied at first, but when your blood sugar goes down, you might become hungry and weak. To prepare for an experience like fasting, fill up on things like pasta, rice, meat, beans, and potatoes instead.
Cut back on activity. When you're fasting, try to take it easy on yourself. Try not to do much strenuous movement or exercise. Your body doesn't have the ability to replenish itself when you're not eating.
Consider medication. Before you start a fast, check with your doctor about any medications you might take. If there are medications you have to take every day, talk with your doctor about whether it's OK to take them without food.
Stop slowly. When you're getting ready to finish your fast, get back to eating slowly. Don't eat a huge meal right away. Instead, spread out your meals and let your body adjust and get used to the process of digesting food again.
Keep in mind that fasting too much or too often can be dangerous and cause dehydration, mental stress, and disrupted sleep.
Also, doctors warn against fasting if you:
- Have diabetes
- Have kidney disease
- Are recovery from surgery or illness
- Are breastfeeding
- Are underweight
Limits of Fasting as a Mood Booster
Even if you fast sometimes, you still need to make healthy food and life choices overall. When you eat is important, but what you eat matters more.
It’s also important to consider that while fasting can be a powerful tool for rejuvenating your mind and body, it's not a substitute for mental health treatment. Talk to a licensed mental health professional if you’re feeling sad or down for long periods of time.