Intermittent fasting is the fastest-growing health lifestyle in the US. But what does the research say? We’ve dug into the research and assembled all the top benefits of intermittent fasting and outlined them system-by-system for the human body.
What Is Intermittent Fasting?
Intermittent fasting is the practice of scheduling your food intake so that you are alternating periods of eating with periods of fasting. There are many different ways to practice intermittent fasting, ranging from a relatively accessible daily fast of 14 hours (of which approximately six are waking) to more challenging fasts of multiple days in length.
There are also many different reasons to fast, with each practitioner having their own rationale for why they do it. While some do, indeed, seek to lose weight or maintain healthier body weight, there are also many other health benefits to be obtained from intermittent fasting.
Intermittent fasting affects the entire body, including the musculoskeletal system, the endocrine system, the digestive system, and the cardiovascular system in particular. After fasting for a certain length of time, typically around 12 hours, you will experience a metabolic switch in which your liver’s glycogen stores are depleted and you begin to use fatty acids for energy instead. Instead of storing fat, your body starts using fat as energy in order to preserve your muscle mass and function. This change in fuel sources, referred to by researchers as the “metabolic switch,” is the main mechanism for the improvements seen from intermittent. It’s effects on improving body composition, as well as other outcomes like enhancing performance and slowing aging can all be traced back to this mechanism, shared by all animals.
One of the things that intermittent fasting can do is improve insulin resistance, which is when cells in your muscles, fat, and liver don’t respond well to insulin and can’t use glucose from your blood for energy. Insulin resistance has been shown to have a link to obstructive sleep apnea, which is when muscles such as your tongue and soft palate relax, temporarily cutting off your breathing and disturbing your sleep. If you suffer from sleep apnea, intermittent fasting could be a possible solution.
Additionally, psychiatric disorders like depression, anxiety, dementia, and mood disorders have been linked with type 2 diabetes, insulin resistance, and cardiovascular disease, all of which may be reduced by intermittent fasting.
Another significant benefit of intermittent fasting is its ability to reduce the risk of Alzheimer’s disease. It does this by stimulating autophagy, a process in which the body recycles cellular waste and eliminates damaged organelles. Because dysregulated autophagy contributes to Alzheimer’s, intermittent fasting’s ability to induce neural autophagy might be a simple, safe, and inexpensive way to protect yourself against Alzheimer’s.
With glucose being your brain’s preferred source of energy, reducing your glucose intake can impact your neurological processes. That being said, hyperglycemia, or having too much sugar in your blood, can also lead to negative neurological outcomes. When you’ve eaten too much sugar, you might experience reduced attention, slower information processing, poorer memory, and more sadness and anxiety. In contrast, lowering your blood sugar through intermittent fasting can improve your focus, mood, and energy levels.
Recent studies have shown that diet is closely tied to acne. In particular, eating a diet lower in sugar (carbohydrates) has been shown to be able to improve both inflammatory and non-inflammatory acne lesions by reducing the size of sebaceous glands, decreasing inflammation, and reducing the expression of certain proteins. One way to eat a diet with a lower glycaemic load is to practice intermittent fasting.
In addition to reducing acne, intermittent fasting’s ability to reduce inflammation by suppressing proinflammatory cytokines and decreasing body fat and circulating levels of leukocytes has also been tied to many positive health outcomes like reducing cancer risk and extending life expectancy.
You’ve probably heard about how important it is to your health to keep your cholesterol levels low, but it’s actually a bit more complicated than that. There are two types of cholesterol: LDL and HDL, with LDL considered bad and HDL considered good. Intermittent fasting has been shown to be able to protect cardiovascular health by raising HDL levels.
Lowers Blood Pressure
Like cholesterol, it is well-known that a relevant factor of health is not having blood pressure that is too high, as this can eventually cause issues such as heart disease. Another impact of intermittent fasting is the ability to decrease blood pressure in people who have elevated blood pressure, even without the use of medication.
As mentioned above, one of the benefits of intermittent fasting is its ability to improve insulin sensitivity, which refers to how sensitive your body’s cells are to insulin. The more sensitive they are, the more effectively your body can use glucose for energy. In contrast, low insulin sensitivity is a risk factor for diabetes.
Reduces Blood Sugar
By increasing your cell’s sensitivity to insulin, intermittent fasting can also reduce your blood sugar. This is because your body will be using the sugar you consume for energy rather than letting lots of excess glucose into your bloodstream, another possible cause of diabetes.
Reduces Risk of Type 2 Diabetes
As you can imagine, its ability to improve insulin sensitivity and reduce blood sugar makes intermittent fasting a very effective way to reduce your risk of type 2 diabetes, which happens when your body has trouble responding to insulin and circulates too much sugar in the blood.
GERD, or gastroesophageal reflux disease, is a digestive disorder that affects the lower esophageal sphincter, causing symptoms like heartburn and indigestion. In the same way that intermittent fasting improves insulin signaling, it has a similar effect on the signaling of other hormones. Intermittent fasting can reduce GERD by improving the signaling of the hunger hormone ghrelin, which has been shown to have an inverse relationship with heartburn.
Another common digestive system issue is IBS, or irritable bowel syndrome, an inflammation of the gastrointestinal system that causes stomach cramps, bloating, diarrhea, and constipation. Studies show that in patients with moderate to severe IBS, intermittent fasting significantly improved many symptoms of IBS including discomfort, diarrhea, nausea, and anxiety.
More and more, science is discovering how impactful the gut microbiome is on one’s general health, with influence on everything from digestive health to mental health. Interestingly, recent evidence has also shown that intermittent fasting can increase the diversity of the microbiome, especially the Lachnospiraceae family of anaerobic bacteria which promote butryogenesis, a process associated with longevity and healthy metabolism.
PCOS, or polycystic ovarian syndrome, is a common disorder associated with infertility and subfertility, as well as metabolic issues like insulin resistance and obesity. It’s been shown that intermittent fasting can reduce certain proteins, as well as glucose and insulin levels, resulting in beneficial effects on ovarian function, androgen excess, and infertility in women with PCOS.
By helping you lose fat and maintain a healthy body weight, intermittent fasting can improve reproductive function, as it has been shown that there is a relationship between obesity, insulin resistance, PCOS, and reproductive disorders. Further, improving insulin resistance can also decrease early pregnancy loss.
Erectile dysfunction (ED) is a sexual disorder plaguing more than half of men. While there are many treatments on the market for this, the totally-free practice of intermittent fasting has been associated with a significantly lower likelihood of having erectile dysfunction, potentially because ED is tied closely to hyperglycemia, something we know can be reduced by intermittent fasting.
Studies have also shown that intermittent fasting can improve total sperm count as well as levels of testosterone and gonadotrophic hormones in fertile males. It also has a beneficial effect on spermatogenesis, all of which means that intermittent fasting is an effective way to improve male fertility.
Remember how intermittent fasting can stimulate autophagy, the cell waste reduction process that helps decrease the risk of diseases like Alzheimer’s? Well, this same process is also known to be related to tumor growth, specifically insofar as autophagy works to suppress tumor growth. Further, animal studies have shown that rats with existing tumors survived longer when intermittent fasting.
Stem cells, the type of cells that all other cells such as blood cells, brain cells, heart muscle cells, and bone cells are created from, can help repair damaged and diseased tissue. But when stem cells get worse at regenerating, something that happens as they age, health issues can result. For example, when your intestinal stem cells start regenerating more poorly, it can make it harder to recover from gastrointestinal issues. But intermittent fasting can reverse the age-related loss of stem cell function, helping your body recover and repair itself better.
Recent evidence shows that bone health and bone turnover issues such as osteoporosis are highly related to inflammation, in that chronic inflammation can weaken bones. But, as noted above, intermittent fasting can improve inflammation by reducing pro-inflammatory cytokines.
Up to 30% of people with psoriasis suffer from psoriatic arthritis, a condition in which joints get swollen, stiff, and painful. This condition has been tied to body mass index, with higher BMI indicating a higher risk for psoriatic arthritis. But research shows that intermittent fasting improved outcomes in a number of rheumatic (related to joints, tendons, ligaments, bones, and muscles) diseases including psoriatic arthritis.
One of the reasons why intermittent fasting is so popular among strength athletes is that it has been shown to be an effective way to lose body weight while retaining muscle mass, meaning that it is more effective for the retention of lean mass while losing fat, something that is usually a concern for dieters seeking to lose weight.
Fibromyalgia is a condition that causes pain all over the body as well as fatigue and emotional and mental distress, making it hard to treat. But studies have shown that a combination of intermittent fasting and a conventional rheumatology approach can significantly improve the symptoms of fibromyalgia, at least in the short term.
One more reason why strength and physique athletes tend to gravitate toward intermittent fasting is that it has been proven to be an effective way to increase levels of HGH, or human growth hormone, which plays an important role in growth, cell regeneration, and cell reproduction.
It is known that intermittent fasting, or achieving a state of temporary starvation, is a very effective way to stimulate autophagy, the process by which the body clears out its old, damaged cells in order to be able to regenerate newer, healthier ones. In fact, this process has even been shown to be tied to lifespan.
Indeed, you may have heard that intermittent fasting can help you live a longer life in addition to what you have probably understood by now will be a healthier one. And research has indeed shown that, in many species, calorie restriction, like in intermittent fasting, can increase maximal lifespan. These same results haven’t been replicated on human test subjects as it’s quite hard to do longevity studies on humans. But if all the other animals it’s been tested on have shown good results, it’s hard to believe that the same wouldn’t apply to humans, as well.
At this point, the vast variety of health benefits of intermittent fasting is clear, but how much of it do you have to do exactly to start experiencing those benefits? Reports vary from person to person, with some sources claiming ten days is enough time to notice a change while others suggest it’s more like ten weeks. Science doesn’t have an answer for us on this, but generally speaking, if you are seeking long-term health benefits, intermittent fasting is something you can view as more of a lifestyle choice than a means to an end.
There are so many different types of intermittent fasting, with fasts of different lengths each having their own benefits to offer. By fasting for only 18 hours, you’ll start to reduce your insulin levels. By 24 hours in, autophagy will begin. If you continue fasting for 48 hours, your body will start to secrete more growth hormone, and within 72 hours, stem cell production may start to be triggered. This isn’t to say that longer fasts are inherently better, but each fasting protocol does have its own effects and benefits.
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