8 Health Benefits of Fasting, Backed by Science

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Fasting may provide several health benefits, including weight loss, blood sugar control, and protection against medical conditions like cancer and neurodegenerative disorders.

Despite its recent surge in popularity, fasting is a practice that dates back centuries and plays a central role in many cultures and religions.

Defined as abstinence from all or some foods or drinks for a set period, there are many different ways of fasting.

Generally, most fasts are performed over 24–72 hours.

Intermittent fasting, on the other hand, involves cycling between periods of eating and fasting, ranging from a few hours to a few days at a time.

Fasting can have health benefits, such as increased weight loss and better brain function.

Here are eight health benefits of fasting — backed by science.

1. Promotes blood sugar control by reducing insulin resistance

Several studies have found that fasting may improve blood sugar control, which may be helpful for those at risk of developing diabetes.

2023 studyTrusted Source of 209 people found intermittent fasting 3 days per week can reduce the risk of type 2 diabetes by increasing insulin sensitivity.

Decreasing insulin resistance can increase your body’s sensitivity to insulin, allowing it to transport glucose from your bloodstream to your cells more efficiently.

Coupled with the potential blood sugar-lowering effects of fasting, this could help keep your blood sugar steady, preventing spikes and crashes in your blood sugar levels.

2022 review of researchTrusted Source notes that intermittent fasting and time-restricted feeding may reduce risk factors associated with metabolic syndrome, a group of five risk factors that increase the likelihood of type 2 diabetes, heart disease, and stroke.

However, additional studies are still needed to compare the effects of fasting with restricting calories.

2. Promotes better health by fighting inflammation

While acute inflammation is a natural immune process used to help fight off infections, chronic inflammation can seriously affect your health.

ResearchTrusted Source shows that inflammation may be involved in the development of chronic conditions, such as heart disease, cancer, and rheumatoid arthritis.

Some studies have found that fasting can help decrease levels of inflammation and promote better health.

One 2022 reviewTrusted Source of 18 studies found that intermittent fasting could significantly reduce levels of C-reactive protein, which is a marker of inflammation.

small studyTrusted Source discovered that practicing intermittent fasting for 1 year was more effective at decreasing levels of inflammation and reducing certain risk factors for heart disease compared to a control group.

3. May enhance heart health by improving blood pressure, triglycerides, and cholesterol levels

Heart disease is considered the leading cause of death worldwide, accounting for an estimated 19 million Trusted Sourcedeaths globally in 2020.

Switching up your diet and lifestyle is one of the most effective ways to reduce your risk of heart disease.

Some research has found that incorporating fasting into your routine may be especially beneficial for heart health.

One reviewTrusted Source revealed that alternate-day fasting could reduce levels of total cholesterol and several risk factors for heart disease in people with overweight compared to a control group.

Another reviewTrusted Source showed that alternate-day fasting could significantly decrease blood pressure, as well as levels of blood triglycerides, total cholesterol, and LDL (bad) cholesterol.

4. May boost brain function and prevent neurodegenerative disorders

Though research is mostly limited to animal research, several studies have found that fasting could have a powerful effect on brain health.

Animal studies from 2018Trusted Source and 2021Trusted Source have reported that fasting could protect brain health and increase the generation of nerve cells to help enhance cognitive function.

Because fasting may also help relieve inflammation, it could also aid in preventing neurodegenerative disorders.

In particular, animal studies suggest that fasting may protect against and improve outcomes for conditions such as Alzheimer’s diseaseTrusted Source and Parkinson’sTrusted Source.

However, more studies are needed to evaluate the effects of fasting on brain function in humans.

5. Aids weight loss by limiting calorie intake and boosting metabolism

Many dieters experiment with fasting to try to lose weight.

Theoretically, abstaining from all or certain foods and beverages should decrease your overall calorie intake, which could lead to increased weight loss over time.

One older reviewTrusted Source from 2015 showed that whole-day fasting could reduce body weight by up to 9% and significantly decrease body fat over 12–24 weeks.

Another reviewTrusted Source found that intermittent fasting was more effective in inducing weight loss compared to continuous calorie restriction.

In addition, other researchTrusted Source has found that fasting may lead to greater reductions in body fat and belly fat compared to continuous calorie restriction.

6. Increases growth hormone secretion, which is vital for growth, metabolism, weight loss, and muscle strength

Human growth hormone (HGH) is a protein hormone central to many aspects of your health.

Research shows that this key hormone is involved in metabolismTrusted Source, weight loss, and muscle growthTrusted Source.

Several studies have found that fasting could naturally increase HGH levels.

One review article noted that fasting for 37.5 hours can increase basal HGH concentrations by as much as ten times and also reduces the metabolic rate at which the body clears HGH.

7. Could extend longevity

Several animal studies have found promising results on the potential lifespan-extending effects of fasting.

One 2021 studyTrusted Source analyzed the effects of periodic fasting on the human gut and found that fasting increased the diversity of helpful bacteria in the gut microbiome, including the Christensenella species, which are related to longevity.

The researchers also noted an increase in sirtuins, proteins involved in metabolic regulation that are also associated with longevity.

2021 reviewTrusted Source of older human and animal research has turned up similar findings, reporting that fasting could be effective in increasing longevity and delaying disease.

However, further studies are needed to understand how fasting may impact longevity and aging in humans and which fasting plans are most effective.

8. May aid in cancer prevention and increase the effectiveness of chemotherapy

reviewTrusted Source published in the American Cancer Society Journal notes that intermittent fasting may benefit the treatment and prevention of cancer in some situations. It may decrease tumor growth and toxicity from chemotherapy in some people.

But they note that more high quality clinical trials are needed and recommend that people undergoing cancer treatment only do intermittent fasting as part of a clinical trial. For some situations and types of cancer, it could potentially have a negative effect.

Another reviewTrusted Source of test tube and animal suggests that fasting could reduce tumor progression and increase chemotherapy’s effectiveness.

Despite these promising findings, additional studies are needed to look at how fasting may influence cancer development and treatment in humans.

How to start fasting

There are many different types of fasts, making it easy to find a method that fits your lifestyle.

Here are a few of the most common types of fasting:

  • Water fasting: Involves drinking only water for a set amount of time.
  • Juice fasting: This entails only drinking vegetable or fruit juice for a certain period.
  • Intermittent fasting: Intake is partially or completely restricted for a few hours up to a few days at a time, and a regular diet is resumed on other days.
  • Partial fasting: Certain foods or drinks such as processed foods, animal products, or caffeine are eliminated from the diet for a set period.
  • Calorie restriction: Calories are restricted for a few days every week.

Within these categories are also more specific types of fasts.

For example, intermittent fasting can be broken down into subcategories, such as alternate-day fasting, which involves eating every other day, or time-restricted feeding, which entails limiting intake to just a few hours each day.

Safety and side effects

Fasting may not be suitable for everyone and may cause side effects.

For example, if you have diabetes, fasting can lead toTrusted Source spikes and crashes in your blood sugar levels, which could be dangerous.

It’s best to talk with a doctor first if you have any underlying health conditions or are planning to fast for more than 24 hours.

Additionally, fasting is not generally recommendedTrusted Source without medical supervision for older adults, adolescents, people with underweight, or people undergoing cancer treatmentTrusted Source.

If you decide to try fasting, be sure to stay well-hydrated and fill your diet with nutrient-dense foods during your eating periods to maximize the potential health benefits.

Additionally, if fasting for longer periods, try to minimize intense physical activity and get plenty of rest.