What Is Fasting? A Guide to the Different Types of Fasts

A fast is a voluntary practice in which people go for extended or structured periods without eating and drinking for spiritual, medical, or weight loss reasons. Others fast to protest or raise awareness for causes. Fasts vary widely depending on the type you’re following. Some fasts allow water, tea, coffee, or other fluids during the fasting period, but dry fasts go without. A fast may be intermittent, or it may extend for multiple days.

Fasting is not starvation. For those who fast for health reasons, fasting is just a more structured way of eating. Fasting is sometimes followed by feasting, especially around religious holidays. Some people may find fasting challenging, but there are many types of fasting regimens and protocols from which to choose.

Many of the world’s major religions and cultures have a rich history of fasting. Fasting has long been promoted as a natural means to boost health and deepen spiritual awareness. In some sects of Buddhism, fasting is a regular part of the monastic lifestyle and enhances meditation. In the Judaeo-Christian and Islamic religious traditions, fasting is an act of observance, atonement, penance, self-control, or preparation for rituals or holidays. Therapeutic fasting dates back to Hippocrates, who prescribed it for many ailments. At the time, it was the only successful way to reduce seizures in epileptic children and remained so until the 20th century.[1]

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Health Benefits of Fasting

Although much of the clinical research related to fasting is limited to animal studies, the abundance of first-hand accounts from people who fast is remarkable, exciting, and encouraging. Many people find that fasting sharpens their mind and provides mental clarity. Interestingly, many of the benefits of fasting don’t result directly from fasting itself, but from the effects of reduced calorie intake, decreased fat composition, better sleep, less diet-related inflammation, and lower intake of salt.

Tempers Blood Pressure and Fluid Balance

Blood pressure tends to fall during the fasting state, primarily during the first week of fasting. This effect seems to result from a lower salt intake and a detoxification of accumulated salt through the urine. Since excess sodium causes your body to retain water, lower sodium levels lead to better fluid balance in your tissues.[1]

Encourages Normal Blood Sugar Levels

Since you don’t need as much insulin while you’re not ingesting sugar, your body’s production of insulin drops during fasting.[2, 3]

Protects the Brain

Fasting and calorie restriction inhibits the production of free radicals and irritating proteins like inflammatory cytokines. Interestingly, evidence suggests that free radical and inflammatory cytokine production slow down during fasting and protective cytokine production increases and protects the brain from oxidative damage.[3]

Moderates Appetite

Fasting causes leptin levels to drop. However, as you lose weight, your response to leptin signaling increases, making it easier to eat healthier foods and smaller portions since you’ll feel more satisfied after a meal.[3] Some weight loss authorities think leptin resistance might be a factor that prevents people who are significantly overweight from dropping pounds because they don’t get that hormonal signal telling them that they’re full.

May Help You Live Longer and Healthier

There is an evolutionary theory that may explain why animals that are fed low-calorie diets tend to live longer than their “well-fed” counterparts. The leading idea holds that when an organism endures challenges like famine, it responds by dedicating more resources to survival.[4] This is kind of like a factory shuffling equipment and labor around to produce a different product while also finding new ways to be more efficient.

Helps Burn Fat

Alternating windows of fasting and eating with regular resistance training leads to greater fat loss than either alone.[5]

Promotes Healthy Immune Function

Fasting triggers the recycling of old white blood cells—the cells that comprise much of your immune system. Recycling these immune cells leads to a more competent immune system. It works by triggering the regeneration of the stem cells that become your platelets, red blood cells, and white blood cells when you begin eating again.[6]

May Increase Resistance to Mental Stress

In animal models, researchers found that the effects of fasting on blood sugar and insulin levels also improves the brain’s response to mental stress and protects it from stress-related damage.[7]

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