What Is Intermittent Fasting
Many diets focus on what to eat, but intermittent fasting is all about when you eat.
With intermittent fasting, you only eat during a specific time. Fasting for a certain number of hours each day or eating just one meal a couple days a week, can help your body burn fat. And scientific evidence points to some health benefits, as well.
Johns Hopkins neuroscientist , has studied intermittent fasting for 25 years. He says that our bodies have evolved to be able to go without food for many hours, or even several days or longer. In prehistoric times, before humans learned to farm, they were hunters and gatherers who evolved to survive and thrive for long periods without eating. They had to: It took a lot of time and energy to hunt game and gather nuts and berries.
Even 50 years ago, it was easier to maintain a healthy weight. Johns Hopkins dietitian Christie Williams, M.S., R.D.N., explains: There were no computers, and TV shows turned off at 11 p.m. people stopped eating because they went to bed. Portions were much smaller. More people worked and played outside and, in general, got more exercise.
Nowadays, TV, the internet and other entertainment are available 24/7. We stay awake for longer hours to catch our favorite shows, play games and chat online. Were sitting and snacking all day and most of the night.
When Is Fasting Not A Good Idea
Fasting is not safe for everyone so consult your physician before you begin.
Those who should not fast include:
- Women who are pregnant or breastfeeding.
- Children and teenagers.
- People who have type 1 diabetes.
- Those who have eating disorders.
Fasting may also have a negative impact on people with other medical problems. Your doctor can help determine whether it is right for you, Dr. Bruemmer says.
Fasting Improves Your Eating Patterns
Fasting can be a helpful practice for those who suffer with binge eating disorders, and for those who find it difficult to establish a correct eating pattern due to work and other priorities.
With intermittent fasting going all afternoon without a meal is okay and it can allow you to eat at a set time that fits your lifestyle. Also, for anyone who wants to prevent binge eating, you can establish a set time in where you allow yourself to eat your daily amount of calories in one sitting, and then not eat till the following day.
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Fasting For Weight Loss
So far, the research studies evaluating intermittent fasting have been relatively short and have enrolled only a limited number of participants. In one, published July 1, 2017, in JAMA Internal Medicine, 100 overweight people were assigned to one of three eating plans: restricting daily calorie intake by the same amount every day , fasting on alternate days, and continuing with normal eating habits. At the end of the 12-month study, both diet groups had lost weight compared with the normal eaters. However, the fasters didn’t fare any better than the conventional calorie cutters.
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 .
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.
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 .
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 (
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 Alzheimers disease and Parkinsons.
Fasting Speeds Up The Metabolism
Intermittent fasting gives your digestive system a rest, and this can energise your metabolism to burn through calories more efficiently. If your digestion is poor, this can effect your ability to metabolise food and burn fat. Intermittent fasts can regulate your digestion and promote healthy bowel function, thus improving your metabolic function.
How Does Intermittent Fasting Help Brain Health
Following a restrictive fasting regimen allows for metabolic switching in the body. Metabolic switching allows the body time to first process stored glucose in the liver and then process fatty acids and ketone bodies. Ketones are not just fuel for the body they also influence factors of brain health and aging. Ketones fuel our brains and have been linked to enhanced thinking, memory, and learning skills.
Recent studies and clinical trials have shown connections to improved memory, executive function, and overall cognition due to regular fasting. Many theorize that this is because those who do not fast never allow their bodies to make a metabolic switch from glycogen to ketones. The late-night snacking and early morning breakfasts that many Americans enjoy could be hindering this process.
Many researchers are studying the possible benefits of fasting among Alzheimers patients. Studies by Mark Mattson, a retired researcher at Johns Hopkins University, indicated that this was the case when he conducted fasting studies on mice. The mice that fasted performed better on cognitive tests than those that did not. However, there is much work to be done to claim these connections as fact.
What Are The Various Types Of Fasting
When pursuing the beneficial effects of fasting, intermittent fasting has maximum benefits.
Table. The way to do intermittent fasting
|Twice a week method|
|The 24-hour fast: eat, stop, eat method|
The Potential Benefits Of Intermittent Fasting
Since the body is unable to get its energy from food during fasting, it dips into glucose that is stored in the liver and muscles. This begins around 8 hours after the last meal is consumed.
When the stored glucose has been used up, the body then begins to burn fat as a source of energy, which can result in weight loss.
As well as aiding weight loss, Dr. Razeen Mahroof, of the University of Oxford in the UK, explains that the use of fat for energy can help preserve muscle and reduce cholesterol levels.
A detoxification process also occurs, because any toxins stored in the bodys fat are dissolved and removed from the body, he adds, noting that after a few days of fasting, higher levels of endorphins feel-good hormones are produced in the blood, which can have a positive impact on mental well-being.
As mentioned previously, the study by Dr. Longo and colleagues suggests prolonged fasting may also be effective for regenerating immune cells.
When you starve, the system tries to save energy, and one of the things it can do to save energy is to recycle a lot of the immune cells that are not needed, especially those that may be damaged, Dr. Longo explains.
In their study, published in the journal Cell Stem Cell, the team found that repeated cycles of 2-4 days without food over a 6-month period destroyed the old and damaged immune cells in mice and generated new ones.
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What Are The Benefits Of Not Being Full All The Time
Regular breaks between eating give our bodies time to carry out valuable housekeeping, according to Dr Collins. After a meal, you absorb the glucose from carbohydrates in food for energy, and either use it immediately or store it for later. In a fasted state, which typically starts 1012 hours after your last meal, the body is depleted of this form of glucose. Then the liver begins to break down stored fat into fatty acids called ketones to use as fuel. This process is known as metabolic switching and is a reason why fasting can lead to weight loss.
But emerging science suggests fasting activates certain chemicals and processes that confer health benefits beyond losing weight. Its also thought to encourage the growth of beneficial gut bacteria that could be good for us in many different ways.
The problem is, most of us are too full for too much of the time to experience these benefits, says Collins. Eating three meals a day plus snacks, as many of us do, means were in a constantly fed state. As a result, our bodies continuously process new intakes of food instead of dealing with fat reserves.
All the things we associate with poor metabolic health and disease risk cardiovascular disease, insulin resistance, diabetes and low energy are essentially a manifestation of fuel mismanagement, he says. Eating in a grazing pattern means youre not able to store, liberate and utilise fuel in the right way.
May Delay Ageing And Support Growth And Metabolism
Fasting, and in particular adopting a diet low in protein, has in animal studies been associated with an extended life expectancy.
Furthermore, fasting appears to promote levels of human growth hormone, a hormone that plays an important role in growth and repair, metabolism, weight loss, muscle strength and exercise performance.
Current longevity research is largely limited to animals, so more studies are needed to fully understand how this may impact human ageing.
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So Is Intermittent Fasting As Good As It Sounds
According to metabolic expert Dr. Deborah Wexler, Director of the Massachusetts General Hospital Diabetes Center and associate professor at Harvard Medical School, says “there is evidence to suggest that the circadian rhythm fasting approach, where meals are restricted to an eight to 10-hour period of the daytime, is effective.” But still she recommends that people “use an eating approach that works for them and is sustainable to them.”
So, heres the deal. There is some good scientific evidence suggesting that circadian rhythm fasting, when combined with a healthy diet and lifestyle, can be a particularly effective approach to weight loss, especially for people at risk for diabetes.
What Can I Eat While Intermittent Fasting
During the times when youre not eating, water and zero-calorie beverages such as black coffee and tea are permitted.
And during your eating periods, eating normally does not mean going crazy. Youre not likely to lose weight or get healthier if you pack your feeding times with high-calorie junk food, super-sized fried items and treats.
But what Williams likes about intermittent fasting is that it allows for a range of different foods to be eaten and enjoyed. We want people to be mindful and take pleasure in eating good, nutritious food, she says. She adds that eating with others and sharing the mealtime experience adds satisfaction and supports good health.
Williams, like most nutrition experts, regards the Mediterranean diet as a good blueprint of what to eat, whether youre trying intermittent fasting or not. You can hardly go wrong when you pick complex, unrefined carbohydrates such as whole grains, leafy greens, healthy fats and lean protein.
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A Better Night’s Sleep
If youve ever felt like you slipped into a food coma after a big meal, you know that diet can have an impact on wakefulness and sleepiness. Some IF followers report being able to sleep better as a result of following this way of eating. IF and mealtimes may have an impact on sleep, Rose-Francis says. Why?
One theory is that IF regulates circadian rhythm, which determines sleep patterns. A regulated circadian rhythm means youll fall asleep easily and wake up feeling refreshed, though research to support this theory is limited, Nature and Science of Sleep.
The other theory centers on the fact that having your last meal earlier in the evening means youll have digested the food by the time you hit the pillow. According to the National Sleep Foundation, digestion is best done when youre upright, and going to sleep with a full stomach can lead to bedtime acid reflux or heartburn, which can make it hard to fall asleep.
Fasting And Weight Loss
If you weed through all the controversy, you’ll find that most medical experts agree on one thing: fasting is not a healthy weight loss tool.
“The appeal is that is quick, but it is quick fluid loss, not substantial weight loss,” says Madelyn Fernstrom, PhD, CNS, founder and director of the University of Pittsburgh Medical Center’s Weight Loss Management Center.
“If it’s easy off, it will come back quickly” — as soon as you start eating normally again, she says.
Even some proponents of fasting for other medical purposes do not support fasting for weight loss. Some say it can actually make weight problems worse.
“Fasting is not a weight loss tool. Fasting slows your metabolic rate down so your diet from before the fast is even more fattening after you fast,” says Joel Fuhrman MD, author of Eat to Live: The Revolutionary Plan for Fast and Sustained Weight Loss and Fasting and Eating for Health.
Fasting for weight loss carries other health risks as well.
While fasting for a day or two is rarely a problem if you are healthy, “it can be quite dangerous if you are not already eating a healthy diet, or if you’ve got liver or kidney problems, any kind of compromised immune system functioning, or are on medication — even Tylenol,” says Fuhrman, a family physician in Flemington, N.J..
In addition, other practices that are often combined with fasting for weight loss, such as colon cleansing, carry their own risks.
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How Does Intermittent Fasting Work
There are several different ways to do intermittent fasting, but they are all based on choosing regular time periods to eat and fast. For instance, you might try eating only during an eight-hour period each day and fast for the remainder. Or you might choose to eat only one meal a day two days a week. There are many different intermittent fasting schedules.
Mattson says that after hours without food, the body exhausts its sugar stores and starts burning fat. He refers to this as metabolic switching.
Intermittent fasting contrasts with the normal eating pattern for most Americans, who eat throughout their waking hours, Mattson says. If someone is eating three meals a day, plus snacks, and theyre not exercising, then every time they eat, theyre running on those calories and not burning their fat stores.
Intermittent fasting works by prolonging the period when your body has burned through the calories consumed during your last meal and begins burning fat.
Fasting Helps Weight Loss
Fasting can be a safe way to lose weight as many studies have shown that intermittent fasting fasting that is controlled within a set number of hours allows the body to burn through fat cells more effectively than just regular dieting.
Intermittent fasting allows the body to use fat as its primary source of energy instead of sugar. Many athletes now use fasting as means to hitting low body fat percentages for competitions.
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Ways To Use This Information For Better Health
Fasting Rejuvenates The Skin And Prevents Acne
If you have been trying cream after cream trying to make your skin look better, you might be surprised to learn that you can achieve the look you want through fasting.
How does this happen? Fasting has a number of effects that help improve your skin.
First and foremost, fasting gives the body a break from digestion, allowing the body to expend more energy on regulating and improving the function of others organs such as the liver, the kidneys, and the skin.
Fasting also helps the body to get rid of toxins that might be contributing to skin conditions.
We have also seen that fasting contributes to autophagy.
This happens to all the cells in the body, including those on your skin.
When you fast, your body regenerates the cells that make up your skin and cleans old cell material from existing cells, thus contributing to a better look.
This regeneration can even contribute to faster healing of scars.
Remember, we also saw that fasting helps reduce inflammation, which is one of the culprits behind some skin conditions like acne. In addition to improving how your skin looks, fasting also contributes to healthy and strong hair and nails and whitens your eyes.
All in all, fasting not only improves how you feel, it also improves how you look.
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