Fasting has been associated with several health benefits, including weight loss, improved blood sugar control, decreased inflammation, and enhanced heart health. It might also offer protection against certain 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 the abstinence from all or some foods or drinks for a set period of time, there are many different ways of fasting.
In general, most types of 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 has been shown to have many health benefits, from increased weight loss to better brain function.
Here are 8 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 could be especially useful for those at risk of diabetes.
In fact, one study in 10 people with type 2 diabetes showed that short-term intermittent fasting significantly decreased blood sugar levels (1Trusted Source).
Meanwhile, another 2014 review found that both intermittent fasting and alternate-day fasting were as effective as limiting calorie intake at reducing insulin resistance (2Trusted Source).
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.
Keep in mind though that some studies have found that fasting may impact blood sugar levels differently for males and females.
For instance, one older, 3-week study showed that practicing alternate-day fasting impaired blood sugar control in females but had no effect in males (3Trusted Source).
2. Promotes better health by fighting inflammation
While acute inflammation is a normal immune process used to help fight off infections, chronic inflammation can have serious consequences for your health.
Research shows that inflammation may be involved in the development of chronic conditions, such as heart disease, cancer, and rheumatoid arthritis (4Trusted Source).
Some studies have found that fasting can help decrease levels of inflammation and promote better health.
One review of 18 studies found that intermittent fasting could significantly reduce levels of C-reactive protein, which is a marker of inflammation (5Trusted Source).
Another small study 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 (6Trusted Source).
What’s more, one animal study found that following a very low calorie diet to mimic the effects of fasting reduced levels of inflammation and was beneficial in the treatment of multiple sclerosis, a chronic inflammatory condition (7Trusted Source).
3. May enhance heart health by improving blood pressure, triglycerides, and cholesterol levels
Heart disease is considered the leading cause of death around the world, accounting for an estimated 31.5% of deaths globally (8Trusted Source).
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 when it comes to heart health.
One review 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 (9Trusted Source).
Another review showed that alternate-day fasting was able to significantly decreased blood pressure, as well as levels of blood triglycerides, total cholesterol, and LDL (bad) cholesterol (10Trusted Source).
In addition, one older study in 4,629 people associated fasting with a lower risk of coronary artery disease, as well as a significantly lower risk of diabetes, which is a major risk factor for heart disease (11Trusted Source).
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.
One 2013 study in mice showed that practicing intermittent fasting for 11 months improved both brain function and brain structure (12Trusted Source).
Other animal studies have reported that fasting could protect brain health and increase the generation of nerve cells to help enhance cognitive function (13Trusted Source, 14Trusted Source).
Because fasting may also help relieve inflammation, it could also aid in preventing neurodegenerative disorders.
In particular, studies in animals suggest that fasting may protect against and improve outcomes for conditions such as Alzheimer’s disease and Parkinson’s (15Trusted Source, 16Trusted 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.
Some research in animals has also found that short-term fasting may boost metabolism by increasing levels of the neurotransmitter norepinephrine, which could enhance weight loss (17Trusted Source).
In fact, one review showed that whole-day fasting could reduce body weight by up to 9% and significantly decrease body fat over 12–24 weeks (18Trusted Source).
Another review found that intermittent fasting was actually more effective in inducing weight loss compared to continuous calorie restriction (19Trusted Source).
In addition, other research has found that fasting may lead to greater reductions in body fat and belly fat compared to continuous calorie restriction (20Trusted Source).
6. Increases growth hormone secretion, which is vital for growth, metabolism, weight loss, and muscle strength
Human growth hormone (HGH) is a type of protein hormone that is central to many aspects of your health (21Trusted Source).
In fact, research shows that this key hormone is involved in metabolism, weight loss, and muscle growth (22Trusted Source, 23Trusted Source, 24Trusted Source).
Several studies have found that fasting could naturally increase HGH levels.
One study in 11 healthy adults showed that fasting for 24 hours significantly increased levels of HGH (25Trusted Source).
Another small, older study in nine males found that fasting for just 2 days led to a five-fold increase in the HGH production rate (26Trusted Source).
Plus, fasting may help maintain steady blood sugar and insulin levels throughout the day, which may further optimize levels of HGH, as some research has found that insulin can influence the secretion of HGH (27Trusted Source).
7. Could extend longevity
Several animal studies have found promising results on the potential lifespan-extending effects of fasting.
In one study, rats that fasted lived 28% longer and developed disease later than rats that were given unlimited access to food (28Trusted Source).
Other research has turned up similar findings, reporting that fasting could be effective in increasing longevity and delaying disease (29Trusted Source).
However, current research is mostly limited to animal studies. Further studies are needed to understand how fasting may impact longevity and aging in humans.
8. May aid in cancer prevention and increase the effectiveness of chemotherapy
Animal and test-tube studies indicate that fasting may benefit the treatment and prevention of cancer (30Trusted Source).
In fact, one older rat study found that alternate-day fasting helped block tumor formation (31Trusted Source).
Other research in test-tubes and animals suggests that fasting could reduce the progression of tumors and increase the effectiveness of chemotherapy (32Trusted Source).
Unfortunately, most research is limited to the effects of fasting on cancer formation in animals and cells.
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: 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 normal 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 (33Trusted Source).
To get started, try experimenting with different types of fasting to find what works best for you.
Safety and side effects
Despite the long list of possible health benefits associated with fasting, it may not be right for everyone.
For example, if you have diabetes, fasting can lead to spikes and crashes in your blood sugar levels, which could be dangerous (34Trusted Source).
It’s best to talk to 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 recommended without medical supervision for older adults, adolescents, or people with underweight (34Trusted 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.
The bottom line
Fasting is a practice that has been associated with a wide array of potential health benefits, including weight loss, as well as improved blood sugar control, heart health, brain function, and cancer prevention.
From water fasting to intermittent fasting and calorie restriction, there are many different types of fasting that fit nearly every lifestyle.
When coupled with a nutritious diet and healthy lifestyle, incorporating fasting into your routine could benefit your health.
