Intermittent fasting is an eating pattern where you cycle between periods of eating and fasting.
Numerous studies show that it can have powerful benefits for your body and brain.
Here are 10 evidence-based health benefits of intermittent fasting.
1. Intermittent Fasting Changes The Function of Cells, Genes and Hormones
When you don’t eat for a while, several things happen in your body.
For example, your body initiates important cellular repair processes and changes hormone levels to make stored body fat more accessible.
Here are some of the changes that occur in your body during fasting:
Insulin levels: Blood levels of insulin drop significantly, which facilitates fat burning (1).
Human growth hormone: The blood levels of growth hormone may increase as much as 5-fold (2, 3). Higher levels of this hormone facilitate fat burning and muscle gain, and have numerous other benefits (4, 5).
Cellular repair: The body induces important cellular repair processes, such as removing waste material from cells (6).
Gene expression: There are beneficial changes in several genes and molecules related to longevity and protection against disease (7, 8).
Many of the benefits of intermittent fasting are related to these changes in hormones, gene expression and function of cells.
BOTTOM LINE:
When you fast, insulin levels drop and human growth hormone increases. Your cells also initiate important cellular repair processes and change which genes they express.
2. Intermittent Fasting Can Help You Lose Weight and Belly Fat
Many of those who try intermittent fasting are doing it in order to lose weight (9).
Generally speaking, intermittent fasting will make you eat fewer meals.
Unless if you compensate by eating much more during the other meals, you will end up taking in fewer calories.
Additionally, intermittent fasting enhances hormone function to facilitate weight loss.
Lower insulin levels, higher growth hormone levels and increased amounts of norepinephrine (noradrenaline) all increase the breakdown of body fat and facilitate its use for energy.
For this reason, short-term fasting actually increases your metabolic rate by 3.6-14%, helping you burn even more calories (10, 11).
In other words, intermittent fasting works on both sides of the calorie equation. It boosts your metabolic rate (increases calories out) and reduces the amount of food you eat (reduces calories in).
According to a 2014 review of the scientific literature, intermittent fasting can cause weight loss of 3-8% over 3-24 weeks (12). This is a huge amount.
The people also lost 4-7% of their waist circumference, which indicates that they lost lots of belly fat, the harmful fat in the abdominal cavity that causes disease.
One review study also showed that intermittent fasting caused less muscle loss than continuous calorie restriction (13).
All things considered, intermittent fasting can be an incredibly powerful weight loss tool. More details here: How Intermittent Fasting Can Help You Lose Weight.
BOTTOM LINE:
Intermittent fasting helps you eat fewer calories, while boosting metabolism slightly. It is a very effective tool to lose weight and belly fat.
3. Intermittent Fasting Can Reduce Insulin Resistance, Lowering Your Risk of Type 2 Diabetes
Type 2 diabetes has become incredibly common in recent decades.
Its main feature is high blood sugar levels in the context of insulin resistance.
Anything that reduces insulin resistance should help lower blood sugar levels and protect against type 2 diabetes.
Interestingly, intermittent fasting has been shown to have major benefits for insulin resistance and lead to an impressive reduction in blood sugar levels (12).
In human studies on intermittent fasting, fasting blood sugar has been reduced by 3-6%, while fasting insulin has been reduced by 20-31% (12).
One study in diabetic rats also showed that intermittent fasting protected against kidney damage, one of the most severe complications of diabetes (13).
What this implies, is that intermittent fasting may be highly protective for people who are at risk of developing type 2 diabetes.
However, there may be some differences between genders. One study in women showed that blood sugar control actually worsened after a 22-day long intermittent fasting protocol (14).
BOTTOM LINE:
Intermittent fasting can reduce insulin resistance and lower blood sugar levels, at least in men.
4. Intermittent Fasting Can Reduce Oxidative Stress and Inflammation in The Body
Oxidative stress is one of the steps towards aging and many chronic diseases (14).
It involves unstable molecules called free radicals, which react with other important molecules (like protein and DNA) and damage them (15).
Several studies show that intermittent fasting may enhance the body’s resistance to oxidative stress (16, 17).
Additionally, studies show that intermittent fasting can help fight inflammation, another key driver of all sorts of common diseases (17, 18, 19).
BOTTOM LINE:
Studies show that intermittent fasting can reduce oxidative damage and inflammation in the body. This should have benefits against aging and development of numerous diseases.
5. Intermittent Fasting May be Beneficial For Heart Health
Heart disease is currently the world’s biggest killer (20).
It is known that various health markers (so-called “risk factors”) are associated with either an increased or decreased risk of heart disease.
Intermittent fasting has been shown to improve numerous different risk factors, including blood pressure, total and LDL cholesterol, blood triglycerides, inflammatory markers and blood sugar levels (12, 21, 22, 23).
However, a lot of this is based on animal studies. The effects on heart health need to be studied a lot further in humans before recommendations can be made.
BOTTOM LINE:
Studies show that intermittent fasting can improve numerous risk factors for heart disease such as blood pressure, cholesterol levels, triglycerides and inflammatory markers.
6. Intermittent Fasting Induces Various Cellular Repair Processes
When we fast, the cells in the body initiate a cellular “waste removal” process called autophagy (7, 24).
This involves the cells breaking down and metabolizing broken and dysfunctional proteins that build up inside cells over time.
Increased autophagy may provide protection against several diseases, including cancer and Alzheimer’s disease (25, 26).
BOTTOM LINE:
Fasting triggers a metabolic pathway called autophagy, which removes waste material from cells.
7. Intermittent Fasting May Help Prevent Cancer
Cancer is a terrible disease, characterized by uncontrolled growth of cells.
Fasting has been shown to have several beneficial effects on metabolism that may lead to reduced risk of cancer.
Although human studies are needed, promising evidence from animal studies indicates that intermittent fasting may help prevent cancer (27, 28, 29, 30).
There is also some evidence on human cancer patients, showing that fasting reduced various side effects of chemotherapy (31).
BOTTOM LINE:
Intermittent fasting has been shown to help prevent cancer in animal studies. One paper in humans showed that it can reduce side effects caused by chemotherapy.
8. Intermittent Fasting is Good For Your Brain
What is good for the body is often good for the brain as well.
Intermittent fasting improves various metabolic features known to be important for brain health.
This includes reduced oxidative stress, reduced inflammation and a reduction in blood sugar levels and insulin resistance.
Several studies in rats have shown that intermittent fasting may increase the growth of new nerve cells, which should have benefits for brain function (32, 33).
It also increases levels of a brain hormone called brain-derived neurotrophic factor (BDNF) (32, 34, 35), a deficiency of which has been implicated in depression and various other brain problems (36).
Animal studies have also shown that intermittent fasting protects against brain damage due to strokes (37).
BOTTOM LINE:
Intermittent fasting may have important benefits for brain health. It may increase growth of new neurons and protect the brain from damage.
9. Intermittent Fasting May Help Prevent Alzheimer’s Disease
Alzheimer’s disease is the world’s most common neurodegenerative disease.
There is no cure available for Alzheimer’s, so preventing it from showing up in the first place is critical.
A study in rats shows that intermittent fasting may delay the onset of Alzheimer’s disease or reduce its severity (38).
In a series of case reports, a lifestyle intervention that included daily short-term fasts was able to significantly improve Alzheimer’s symptoms in 9 out of 10 patients (39).
Animal studies also suggest that fasting may protect against other neurodegenerative diseases, including Parkinson’s and Huntington’s disease (40, 41).
However, more research in humans is needed.
BOTTOM LINE:
Studies in animals suggest that intermittent fasting may be protective against neurodegenerative diseases like Alzheimer’s disease.
10. Intermittent Fasting May Extend Your Lifespan, Helping You Live Longer
One of the most exciting applications of intermittent fasting may be its ability to extend lifespan.
Studies in rats have shown that intermittent fasting extends lifespan in a similar way as continuous calorie restriction (42, 43).
In some of these studies, the effects were quite dramatic. In one of them, rats that fasted every other day lived 83% longer than rats who weren’t fasted (44).
Although this is far from being proven in humans, intermittent fasting has become very popular among the anti-aging crowd.
Given the known benefits for metabolism and all sorts of health markers, it makes sense that intermittent fasting could help you live a longer and healthier life.
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 (1).
Meanwhile, another review found that both intermittent fasting and alternate-day fasting were as effective as limiting calorie intake at reducing insulin resistance (2).
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 men and women.
For instance, one small, three-week study showed that practicing alternate-day fasting impaired blood sugar control in women but had no effect in men (3).
SUMMARY
Intermittent fasting and alternate-day fasting could help decrease blood sugar levels and reduce insulin resistance but may affect men and women differently.
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 (4).
Some studies have found that fasting can help decrease levels of inflammation and help promote better health.
One study in 50 healthy adults showed that intermittent fasting for one month significantly decreased levels of inflammatory markers (5).
Another small study discovered the same effect when people fasted for 12 hours a day for one month (6).
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 (7).
SUMMARY
Some studies have found that fasting could decrease several markers of inflammation and may be useful in treating inflammatory conditions, such as multiple sclerosis.
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 (8).
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 small study revealed that eight weeks of alternate-day fasting reduced levels of “bad” LDL cholesterol and blood triglycerides by 25% and 32% respectively (9).
Another study in 110 obese adults showed that fasting for three weeks under medical supervision significantly decreased blood pressure, as well as levels of blood triglycerides, total cholesterol and “bad” LDL cholesterol (10).
In addition, one 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 (11).
SUMMARY
Fasting has been associated with a lower risk of coronary heart disease and may help lower blood pressure, triglycerides and cholesterol levels.
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 study in mice showed that practicing intermittent fasting for 11 months improved both brain function and brain structure (12).
Other animal studies have reported that fasting could protect brain health and increase the generation of nerve cells to help enhance cognitive function (13, 14).
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 (15, 16).
However, more studies are needed to evaluate the effects of fasting on brain function in humans.
SUMMARY
Animal studies show that fasting could improve brain function, increase nerve cell synthesis and protect against neurodegenerative conditions, such as Alzheimer’s disease and Parkinson’s.
5. Aids Weight Loss by Limiting Calorie Intake and Boosting Metabolism
Many dieters pick up fasting looking for a quick and easy way to drop a few pounds.
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 has also found that short-term fasting may boost metabolism by increasing levels of the neurotransmitter norepinephrine, which could enhance weight loss (17).
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 (18).
Another review found that intermittent fasting over 3–12 weeks was as effective in inducing weight loss as continuous calorie restriction and decreased body weight and fat mass by up to 8% and 16% respectively (19).
In addition, fasting was found to be more effective than calorie restriction at increasing fat loss while simultaneously preserving muscle tissue (19).
SUMMARY
Fasting may increase metabolism and help preserve muscle tissue to reduce body weight and body fat.
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.
In fact, research shows that this key hormone is involved in growth, metabolism, weight loss and muscle strength (20, 21, 22, 23).
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 (24).
Another small study in nine men found that fasting for just two days led to a 5-fold increase in the HGH production rate (25).
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 sustaining increased levels of insulin may reduce HGH levels (26).
SUMMARY
Studies show that fasting can increase levels of human growth hormone (HGH), an important protein hormone that plays a role in growth, metabolism, weight loss and muscle strength.
7. Could Delay Aging and Extend Longevity
Several animal studies have found promising results on the potential lifespan-extending effects of fasting.
In one study, rats that fasted every other day experienced a delayed rate of aging and lived 83% longer than rats that didn’t fast (27).
Other animal studies have had similar findings, reporting that fasting could be effective in increasing longevity and survival rates (28, 29, 30).
However, current research is still limited to animal studies. Further studies are needed to understand how fasting may impact longevity and aging in humans.
SUMMARY
Animal studies have found that fasting could delay aging and increase longevity, but human research is still lacking.
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.
In fact, one rat study found that alternate-day fasting helped block tumor formation (31).
Similarly, a test-tube study showed that exposing cancer cells to several cycles of fasting was as effective as chemotherapy in delaying tumor growth and increased the effectiveness of chemotherapy drugs on cancer formation (32).
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.
SUMMARY
Some animal and test-tube studies suggest that fasting could block tumor development and increase the effectiveness of chemotherapy.
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.
To get started, try experimenting with different types of fasting to find what works best for you.
SUMMARY
There are many different ways to practice fasting, which makes it easy to find a method that fits into just about any lifestyle. Experiment with different types 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.
If you suffer from diabetes or low blood sugar, fasting can lead to spikes and crashes in your blood sugar levels, which could be dangerous.
It’s best to talk to your 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 who are underweight.
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.
SUMMARY
When fasting, be sure to stay hydrated, eat nutrient-dense foods and get plenty of rest. It’s best to consult with your doctor before fasting if you have any underlying health conditions or are planning to fast for more than 24 hours.
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.
