Gunnars K. Healthline.
May 13, 2021
Intermittent fasting is an eating pattern where you cycle between periods of eating and fasting.
There are many different types of intermittent fasting, such as the 16/8 and 5:2 methods.
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. Changes the function of hormones, cells, and genes
When you don’t eat for a while, several things happen in your body.
For example, your body changes hormone levels to make stored body fat more accessible and initiates important cellular repair processes.
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.
Human growth hormone (HGH) levels. The blood levels of human growth hormone (HGH) may increase dramatically. Higher levels of this hormone facilitate fat burning and muscle gain, and have numerous other benefits.
Cellular repair. The body induces important cellular repair processes, such as removing waste material from cells.
Gene expression. There are beneficial changes in several genes and molecules related to longevity and protection against disease.
Many of the benefits of intermittent fasting are related to these changes in hormones, the function of cells, and gene expression.
When you fast, insulin levels drop and human growth hormone (HGH) increases. Your cells also initiate important cellular repair processes and change which genes they express.
2. Can help you lose weight and visceral fat
Many of those who try intermittent fasting are doing it to lose weight.
Generally speaking, intermittent fasting will make you eat fewer meals.
Unless you compensate by eating much more during the other meals, you’ll end up taking in fewer calories.
Additionally, intermittent fasting enhances hormone function to facilitate weight loss.
Lower insulin levels, higher HGH 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, helping you burn even more calories.
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. This is a huge amount.
The study participants also lost 4–7% of their waist circumference over 6–24 weeks, which indicates that they lost lots of visceral fat. Visceral fat is the harmful fat in the abdominal cavity that causes disease.
One 2011 review also showed that intermittent fasting caused less muscle loss than continuous calorie restriction.
However, a 2020 randomized trial looked at people who followed the 16/8 method. In this diet, you fast for 16 hours a day and have an 8-hour window to eat.
The people who fasted didn’t lose significantly more weight than the people who ate three meals a day. After testing a subset of the participants in person, the researchers also found that the people who fasted lost a significant amount of lean mass. This included lean muscle.
More studies are needed on the effect of fasting on muscle loss. All things considered, intermittent fasting has the potential to be an incredibly powerful weight loss tool.
Intermittent fasting helps you eat fewer calories while boosting metabolism slightly. It’s a very effective tool to lose weight and visceral fat.
3. Can reduce insulin resistance, lowering your risk for type 2 diabetes
Type 2 diabetes has become a very common diagnosis 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 to lead to an impressive reduction in blood sugar levels.
In human studies on intermittent fasting, fasting blood sugar has been reduced by 3–6% over the course of 8–12 weeks in people with prediabetes. Fasting insulin has been reduced by 20–31%.
One study in mice with diabetes also showed that intermittent fasting improved survival rates and protected against diabetic retinopathy. Diabetic retinopathy is a complication that can lead to blindness.
What this implies is that intermittent fasting may be highly protective for people who are at risk for developing type 2 diabetes.
However, there may be some differences between the sexes. One 2005 study in women showed that blood sugar management actually worsened after a 22-day long intermittent fasting protocol.
Intermittent fasting can reduce insulin resistance and lower blood sugar levels, at least in men.
4. Can reduce oxidative stress and inflammation in the body
Oxidative stress is one of the steps toward aging and many chronic diseases.
It involves unstable molecules called free radicals. Free radicals react with other important molecules, such as protein and DNA, and damage them.
Several studies show that intermittent fasting may enhance the body’s resistance to oxidative stress.
Additionally, studies show that intermittent fasting can help fight inflammation, another key driver of many common diseases.
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. May be beneficial for heart health
Heart disease is currently the world’s biggest killer.
It’s 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 sugar levels
total and LDL (bad) cholesterol
However, much of this is based on animal studies.
The effects of fasting on heart health need to be studied more in-depth in humans before recommendations can be made.
Studies show that intermittent fasting can improve numerous risk factors for heart disease, such as blood pressure, cholesterol levels, triglycerides, and inflammatory markers.
6. Induces various cellular repair processes
When we fast, the cells in the body initiate a cellular “waste removal” process called autophagy.
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 neurodegenerative diseases such as Alzheimer’s disease.
Fasting triggers a metabolic pathway called autophagy, which removes waste material from cells.
7. May help prevent cancer
Cancer is 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.
Promising evidence from animal studies indicates that intermittent fasting or diets that mimic fasting may help prevent cancer. Research in humans has led to similar findings, although more studies are needed.
There’s also some evidence showing that fasting reduced various side effects of chemotherapy in humans.
Intermittent fasting has been shown to help prevent cancer in animal studies and some human studies. Research in humans showed that it can help reduce side effects caused by chemotherapy.
8. Has benefits for your brain
What’s 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.
Intermittent fasting helps reduce:
blood sugar levels
Several studies in mice and rats have shown that intermittent fasting may increase the growth of new nerve cells, which should have benefits for brain function.
Fasting also increases levels of a brain hormone called brain-derived neurotrophic factor (BDNF). A BDNF deficiency has been implicated in depression and various other brain problems.
Animal studies have also shown that intermittent fasting protects against brain damage due to strokes.
Intermittent fasting may have important benefits for brain health. It may increase growth of new neurons and protect the brain from damage.
9. May help prevent Alzheimer’s disease
Alzheimer’s disease is the world’s most common neurodegenerative disease.
There’s no cure currently available for Alzheimer’s, so preventing it from showing up in the first place is critical.
Studies in rats and mice show that intermittent fasting may delay the onset of Alzheimer’s or reduce its severity.
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 people.
Animal studies also suggest that fasting may protect against other neurodegenerative diseases, including Parkinson’s disease and Huntington’s disease.
However, more research in humans is needed.
Studies in animals suggest that intermittent fasting may be protective against neurodegenerative diseases such as Alzheimer’s disease.
10. 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 rodents have shown that intermittent fasting extends lifespan in a similar way as continuous calorie restriction.
Intermittent fasting has also been shown to increase the lifespans of fruit flies.
In some of these studies, the effects were quite dramatic. In an older study, rats that were fasted every other day lived 83% longer than rats who weren’t fasted.
In a 2017 study, mice that were fasted every other day saw their lifespans increase by around 13%.
Daily fasting was also shown to improve the overall health of male mice. It helped delay the onset of conditions such as fatty liver disease and hepatocellular carcinoma, which are both common in aging mice.
Although this is far from being determined 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.
Intermittent fasting may help you live longer, according to studies in animals.
The bottom line
Intermittent fasting is a very popular weight-loss method, but its benefits extend beyond that. It can help you live a longer and all-around healthier life too, according to studies involving animals and humans.
There are many ways to practice intermittent fasting. Some methods involve fasting during certain hours each day. Other methods only require you to fast on certain days of the week. Approaches — and results — vary.
If you’re interested in starting intermittent fasting, consider speaking with your doctor or a nutrition expert today. They can help you determine whether it’s safe for you.
Last medically reviewed on May 13, 2021
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