Is fasting healthy?

CAIRO – 14 April 2022: While many people around the world fast for religious and cultural reasons, there are others who believe fasting has scientifically proven health benefits, as long as you do it safely.

There are many different types of fasting, explains Andrew Wang, MD, professor of immunobiology at Yale University School of Medicine, and the most well-known of these is intermittent fasting.

Benefits of fasting

Fasting has many mental and physical health benefits, the most important of which are:

1. Reducing inflammation: One of the most important benefits of fasting is that it reduces inflammation, which is the body's natural response to infection and usually disappears after damaged cells heal. However, when the body is exposed to oxidative stress, a process caused by the buildup of free radicals, it can enter a state of chronic inflammation. This is because these free radicals, which can come from external sources such as pollution and bodily processes (such as digestion) begin to attack healthy tissues and cells. Chronic inflammation can damage healthy cells, tissues and organs, and is linked to many diseases, including heart attacks and strokes. 

There are several ways to reduce inflammation in the body through fasting:

When your body is in a fasting state, it cannot convert glucose from food into energy. Instead, your body relies on an alternative energy source called ketone bodies, which come from fatty acids. Your body produces fewer free radicals when burning ketones, which helps reduce inflammation. Fasting may also reduce inflammation by reducing the number of monocytes, a type of inflammatory white blood cells, in the bloodstream.

2. Enhancing Cognitive Performance: As we age, our organs are prone to chronic inflammation, says Wang. Chronic inflammation can contribute to cognitive decline and possible dementia due to plaque buildup in the brain. Wang notes that fasting helps counter this by reducing inflammation. There is a growing body of research suggesting that fasting can prevent the development of Alzheimer's disease in animals. A 2019 study found that intermittent fasting can slow cognitive decline and improve Alzheimer's disease symptoms in mice. Fasting can improve mental flexibility, which is defined as the ability to switch quickly and efficiently between tasks.

3. Regulating blood sugar levels: Fasting may also regulate blood sugar levels, which is important for protecting against diseases such as type 2 diabetes. Wang says blood sugar increases when you eat, so it naturally drops when you fast. However, your body will prevent your blood sugar from dropping too low by making glucose itself. This keeps blood sugar at healthy levels.

4. Improving heart health: While research on the topic is limited, Wang says it's reasonable to assume that fasting promotes heart health by reducing inflammation and protecting against diabetes, both of which are risk factors for heart attacks and strokes. 

5. Contributing in losing weight: Fasting helps you lose weight by limiting the number of calories you eat. Intermittent fasting, in particular, helps with weight loss by keeping blood sugar levels low in the evening when you are less active. 

However, there is mixed evidence about whether fasting for weight loss is more effective than a calorie-restricted diet. If you want to lose weight, talk to your doctor about the method that works best for you.

How to fast safely?

While intermittent fasting usually involves fasting for 16 hours a day, longer fasts can range from 24 to 72 hours. "There is no magic amount of time you should fast," says Wang. The best thing you can do is listen to your body and decide what type of fasting is right for you. If you feel jittery, nauseous or faint while fasting, you should consider breakfast. 

Wang cautions that there are specific groups that should refrain from fasting, which include pregnant women, those who breastfeed their children, those with a history of eating disorders, as well as those with diabetes or blood sugar problems.