Intermittent fasting has become a popular dietary approach to help people lose or manage their weight. It has also been promoted as a way to reset metabolism, control chronic disease, slow aging and improve overall health.
Meanwhile, some research suggests intermittent fasting may offer a different way for the brain to access energy and provide protection against neurodegenerative diseases like Alzheimer’s disease.
This is not a new idea—the ancient Greeks believed fasting enhanced thinking. But what does the modern-day evidence say?
First, what is intermittent fasting?
Our diets—including calories consumed, macronutrient composition (the ratios of fats, protein and carbohydrates we eat) and when meals are consumed—are factors in our lifestyle we can change. People do this for cultural reasons, desired weight loss or potential health gains.
Intermittent fasting consists of short periods of calorie (energy) restriction where food intake is limited for 12 to 48 hours (usually 12 to 16 hours per day), followed by periods of normal food intake. The intermittent component means a re-occurrence of the pattern rather than a “one off” fast.
Food deprivation beyond 24 hours typically constitutes starvation. This is distinct from fasting due to its specific and potentially harmful biochemical alterations and nutrient deficiencies if continued for long periods.
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The brain accounts for about 20% of the body’s energy consumption.
Here are four ways intermittent fasting can act on the body which could help explain its potential effects on the brain.
4 ways fasting works and how it might affect the brain.
1. Ketosis
The goal of many intermittent fasting routines is to flip a “metabolic switch” to go from burning predominately carbohydrates to burning fat. This is called ketosis and typically occurs after 12–16 hours of fasting, when liver and glycogen stores are depleted. Ketones—chemicals produced by this metabolic process—become the preferred energy source for the brain.
Due to this being a slower metabolic process to produce energy and potential for lowering blood sugar levels, ketosis can cause symptoms of hunger, fatigue, nausea, low mood, irritability, constipation, headaches, and brain “fog”.
At the same time, as glucose metabolism in the brain declines with aging, studies have shown ketones could provide an alternative energy source to preserve brain function and prevent age-related neurodegeneration disorders and cognitive decline.
Consistent with this, increasing ketones through supplementation or diet has been shown to improve cognition in adults with mild cognitive decline and those at risk of Alzheimer’s disease respectively.
2. Circadian syncing
Eating at times that don’t match our body’s natural daily rhythms can disrupt how our organs work. Studies in shift workers have suggested this might also make us more prone to chronic disease.
Time-restricted eating is when you eat your meals within a six to ten-hour window during the day when you’re most active. Time-restricted eating causes changes in expression of genes in tissue and helps the body during rest and activity.A 2021 study of 883 adults in Italy indicated those who restricted their food intake to ten hours a day were less likely to have cognitive impairment compared to those eating without time restrictions.
3. Mitochondria
Intermittent fasting may provide brain protection through improving mitochondrial function, metabolism and reducing oxidants.
Mitochondria’s main role is to produce energy and they are crucial to brain health. Many age-related diseases are closely related to an energy supply and demand imbalance, likely attributed to mitochondrial dysfunction during aging.
Fasting or reducing calories by up to 40% might protect or improve brain mitochondrial function. But not all studies support this theory.
4. The gut-brain axis
The gut and the brain communicate with each other via the body’s nervous systems. The brain can influence how the gut feels (think about how you get “butterflies” in your tummy when nervous) and the gut can affect mood, cognition and mental health.
In mice, intermittent fasting has shown promise for improving brain health by increasing survival and formation of neurons (nerve cells) in the hippocampus brain region, which is involved in memory, learning and emotion.
There’s no clear evidence on the effects of intermittent fasting on cognition in healthy adults. However one 2022 study interviewed 411 older adults and found lower meal frequency (less than three meals a day) was associated with reduced evidence of Alzheimer’s disease on brain imaging.
Some research has suggested calorie restriction may have a protective effect against Alzheimer’s disease by reducing oxidative stress and inflammation and promoting vascular health.
When we look at the effects of overall energy restriction (rather than intermittent fasting specifically) the evidence is mixed. Among people with mild cognitive impairment, one study showed cognitive improvement when participants followed a calorie restricted diet for 12 months.
Another study found a 25% calorie restriction was associated with slightly improved working memory in healthy adults. But a recent study, which looked at the impact of calorie restriction on spatial working memory, found no significant effect.
Bottom line
Studies in mice support a role for intermittent fasting in improving brain health and aging, but few studies in humans exist, and the evidence we have is mixed.
Rapid weight loss associated with calorie restriction and intermittent fasting can lead to nutrient deficiencies, muscle loss, and decreased immune function, particularly in older adults whose nutritional needs may be higher.
Further, prolonged fasting or severe calorie restriction may pose risks such as fatigue, dizziness, and electrolyte imbalances, which could exacerbate existing health conditions.
If you’re considering intermittent fasting, it’s best to seek advice from a health professional such as a dietitian who can provide guidance on structuring fasting periods, meal timing, and nutrient intake. This ensures intermittent fasting is approached in a safe, sustainable way, tailored to individual needs and goals.This article is republished from The Conversation under a Creative Commons license. Read the original article.
Provided by The ConversationThis story was originally published on Medical Xpress. Subscribe to our newsletter for the latest sci-tech news updates.Does intermittent fasting have benefits for our brain?
What Is Intermittent Fasting and How Does It Work?
Intermittent fasting is an eating pattern that may benefit heart health, reduce inflammation, improve cell repair processes, and help burn fat.
Intermittent fasting is an eating pattern in which you cycle between periods of eating and periods of fasting.
There are many types of intermittent fasting, such as the 16:8 and 5:2 methods.Numerous studies suggest that it can have powerful benefits for your body and brain.Here are 10 evidence-based health benefits of intermittent fasting.
1. Changes in 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 starts important cellular repair processes.
Here are some of the changes that may happen in your body as a result of intermittent fasting:
Insulin level: Your blood level of insulin drops significantly, which promotes fat burning.Human growth hormone (HGH) level: Your blood level of HGH may increase dramatically. Higher levels of this hormone promote fat burning and muscle gain and have numerous other benefits.
Cellular repair: Your body starts important cellular repair processes such as removing waste material from cells.Gene expression: Beneficial changes occur 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, cellular function, and gene expression.
2. Can help you lose weight and visceral fat
Many people try intermittent fasting in an effort to lose weight.
Generally, 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 promote weight loss. Lower insulin levels, higher HGH levels, and increased levels of norepinephrine all increase the breakdown of body fat and make it easier for your body to use fat for energy.
For this reason, short-term fasting actually improves your metabolism, helping you burn even more calories.
In a 2022 study involving 131 people with obesity, researchers found that those who participated in 12 weeks of intermittent fasting lost an average of 9% of their body weight — more than those who engaged in other weight loss methods.
But this study focused on the 5:2 intermittent fasting plan, which means the participants ate normally for 5 days and restricted their calories for 2 days each week
.The authors of a 2020 review of 27 studies noted that participants doing intermittent fasting lost 0.8–13% of their baseline body weight.
In a 2020 trial, researchers focused on people who followed the 16:8 method, which involves fasting for 16 hours per day and eating within an 8-hour window.
The people who fasted didn’t lose significantly more weight than those who ate three meals per day. But after testing a subset of the participants in person, the researchers found that those who fasted had lost a significant amount of lean mass, including lean muscle.
More studies are needed to investigate the effect of fasting on muscle loss. But, all things considered, intermittent fasting has the potential to be an incredibly powerful weight loss too.
SUMMARY
When you fast, your insulin level drops and your HGH level increases. Your cells also start important cell repair processes and change which genes they express.
Intermittent fasting helps you eat fewer calories while slightly boosting your metabolism. It’s a very effective tool for losing weight and visceral fat.
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3. Can reduce insulin resistance, lowering your risk for type 2 diabetes
Intermittent fasting has been shown to have major benefits for insulin resistance and to lead to an impressive reduction in blood sugar levels.
Anything that reduces insulin resistance should help lower your blood sugar levels and protect against type 2 diabetes.
In a 2022 review of 10 studies on intermittent fasting, the authors concluded that fasting blood sugar was reduced by an average of 0.15 millimoles per liter.
A 2018 study in mice with diabetes also showed that intermittent fasting improved survival rates and protected against diabetic retinopathy, a diabetes complication that can lead to blindness.These results suggest 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 the effects in men and women. One 2015 study, as reported in a 2017 meta-analysis, showed that blood sugar regulation in women actually worsened after a 3-week intermittent fasting protocol, whereas men experienced an improvement in blood sugar regulation.
SUMMARY
Intermittent fasting can reduce insulin resistance and lower blood sugar levels, at least in men.
4. Can reduce oxidative stress and inflammation in your body
Oxidative stress is one factor that can contribute to aging and many chronic diseases.It involves unstable molecules called free radicals, which react with other important molecules, such as protein and DNA, and damage them.
According to a 2018 review, intermittent fasting may enhance your body’s resistance to oxidative stress.Additionally, a 2019 study suggests that intermittent fasting can help fight inflammation, another key driver of many common diseases.
SUMMARY
Studies suggest that intermittent fasting can reduce oxidative damage and inflammation in your body, leading to benefits related to aging and the development of numerous diseases.
5. May be beneficial for heart health
Heart disease is currently the world’s top cause of death.
Various health markers, known as risk factors, are associated with either an increased or decreased risk of heart disease.
Intermittent fasting has been shownTrusted Source to improve several risk factors for heart disease, including:
- blood sugar levels
- blood pressure
- blood triglycerides
- total and LDL (bad) cholesterol
- inflammatory markers
SUMMARY
Research shows that intermittent fasting can improve many risk factors for heart disease, including blood pressure, cholesterol levels, triglyceride levels, and inflammatory markers.
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6. Induces various cellular repair processes
When you fast, the cells in your body start a cellular waste removal process called autophagy.
In this process, the cells break down and metabolize broken and dysfunctional proteins that build up inside them over time.
Increased autophagy may provide protection against several diseases, including cancer and neurodegenerative diseases such as Alzheimer’s disease.
SUMMARY
Fasting triggers a metabolic pathway called autophagy, which removes waste material from cells.
7. May help prevent cancer
Cancer involves 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 suggests that intermittent fasting or diets that mimic fasting may help prevent cancer.
However, research in humans has had inconsistent findings, and more research is needed to help health experts understand how intermittent fasting might affect cancer risk.
There’s also some evidence that fasting may reduce the side effects of chemotherapy in some cases.
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SUMMARY
Intermittent fasting has been shown to help prevent cancer in animal studies and some human studies. Research in humans also suggests that intermittent fasting can help reduce side effects of chemotherapy.
8. Has benefits for your brain
What’s good for your body is often good for your brain as well.
Intermittent fasting improves various metabolic features known to be important for brain health.
Intermittent fasting can help reduce:
- oxidative stress
- inflammation
- blood sugar levels
- insulin resistance
Animal research has shown that intermittent fasting may increase the growth of new nerve cells, which could have benefits for brain function.
Fasting also increases levels of a brain hormone called brain-derived neurotrophic factor (BDNF). A BDNF deficiency may be involved in depression and other brain conditions.
Additionally, research suggests that intermittent fasting may help protect against brain damage due to stroke.
SUMMARY
Intermittent fasting may have important benefits for brain health, including increasing growth of new neurons and protecting your brain from damage.
9. May help prevent Alzheimer’s disease
Alzheimer’s disease is the world’s most common neurodegenerative disease.
There’s currently no cure for Alzheimer’s, so preventing it from developing in the first place is critical.
The authors of a 2023 review concluded that intermittent fasting may help delay the onset of Alzheimer’s or reduce its severity.
Animal studies also suggest that fasting may protect against other neurodegenerative diseases, including Parkinson’s disease and Huntington’s disease.
10. May help you live longer
One of the most exciting applications of intermittent fasting may be its potential to extend life span.
Research in rodents has shown that intermittent fasting extends life span in a similar way to continuous calorie restriction.
In a 2017 study, mice that fasted every other day had about a 13% increase in life span.
Daily fasting has also been shown to improve the overall health of male mice. In a 2019 study, it helped delay the onset of conditions such as fatty liver disease and hepatocellular carcinoma, both of which are common in aging mice.
Additionally, intermittent fasting has been found to increase the life span of fruit flies.
While researchers have not yet determined that fasting has the same effect in humans, intermittent fasting has become very popular in anti-aging circles.
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.
Frequently asked questions
Why is 16 hours the magic number for fasting?
Fasting for 16 hours a day can be an effective way to lose weight. That said, according to a 2022 review, alternating your fasting days might actually be more effective than the 5:2 diet or time-restricted eating such as the 16:8 diet.
What are the benefits of 16:8 intermittent fasting?
Fasting for 16 hours and eating for 8 hours every day may help you lose weight, lower your blood sugar, and have other positive effects on your body that may be associated with a longer life span. However, more research is needed to find out whether this is the case.
What happens if I do intermittent fasting every day?
Generally, following an intermittent fasting diet, every day may have a positive impact on your overall health and your weight. But you might experience some negative side effects such as lethargy, headaches, and constipation. You also need to be careful not to overeat during the eating window.
Intermittent fasting is a very popular weight loss method, but its benefits extend beyond that. It may help you live a longer and all-around healthier life, 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 require fasting on only some days of the week. Approaches — and results — vary.
If you’re interested in starting intermittent fasting, consider speaking with a doctor or a registered dietitian. They can help you decide whether it’s safe for you. Be sure to discuss any medications you’re taking, as some could cause negative side effects if you fast.
SUMMARY
Intermittent fasting may help you live longer, according to studies in animals.
However, more research in humans is needed.
SUMMARY
Studies in animals suggest that intermittent fasting may help protect against neurodegenerative diseases such as Alzheimer’s disease.
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