Curious about fasting? Here's the ultimate guide.
Fasting is the practice of abstaining or reducing consumption of food, drink or both, for a specific period of time. Everyone fasts for at least some part of the day, generally the eight or so hours one spends sleeping every night. Physiologically, fasting can refer to a person’s metabolic status after not eating overnight, or even the metabolic state after the complete digestion of a meal. Once you’ve gone eight to 12 hours without eating, the body enters a state of “fasting.”
The practice of fasting can lead to a number of metabolic changes within the body. These changes typically begin approximately three to five hours after eating, when the body enters a post-absorptive state, as opposed to the state of ongoing digestion. Eating frequent meals means the body is always involved in some sort of digestive activity.
Whether you practice more long-term fasting for health reasons or for spiritual reasons, most people will have to fast at some point for medical reasons. Patients undergoing surgery or other medical procedures that require a general anaesthetic will usually fast prior to the treatment, but fasting is also practiced before a number of other medical tests, including cholesterol testing, blood glucose measuring or a lipid panel. This enables doctors to achieve accurate results and establish a solid baseline to inform future testing, if necessary.
Here are 15 amazing benefits of intermittent fasting.
1. Weight loss
Instead of running on fuel from the food you just ate, fasting allows your body to tap into reserves—fat, which accumulates on the body to be burned whenever food supply grows scarce. This results in a slow, steady weight loss that can be a huge benefit.
Since fasting is often incorporated as a lifestyle change instead of a temporary fix, this type of diet is much more sustainable than many other “crash diets.” In fact, many studies support the practice as a valuable, reliable tool for weight loss and weight maintenance. Initially, you’ll see a marked weight loss as a result of losing water weight, but according to the author of Eat Stop Eat, each day you fast will show a loss of 0.5 pounds of true body fat.
2. Improved tolerance of glucose
For diabetics, fasting can be a fantastic way to normalize glucose and even improve glucose variability. Anyone looking for a natural way to increase insulin sensitivity should attempt an intermittent fast, as the effects of fasting can make a huge difference in how your body processes glucose.
Generally, insulin resistance is the result of accumulation of glucose in tissues that aren’t built for fat storage. As the body burns through stored fuel in the form of body fat, that excess accumulation becomes smaller and smaller, allowing the cells in your muscles and liver to grow increasingly responsive to insulin—great news for anyone looking to be less dependent on medications to assist these processes.
3. Boosts metabolism
Part of the reason intermittent fasting helps practitioners lose weight is because the restriction of food, followed by regular eating, can help stimulate your metabolism. While long-term fasting can actually cause a drop in your metabolism, the shorter fasts promoted by intermittent fasting have proven to increase metabolism by up to 14 percent, reported by one study.
This is also a more effective tool than long-term calorie restriction, which can often wreak havoc on the body’s metabolism. Weight loss often goes hand in hand with muscle loss, and since muscle tissue is what burns through calories, having less muscle leads to a drop in your body’s ability to metabolize food. Intermittent fasting, though, keeps your metabolism running smoothly by helping you maintain your muscle tissue as much as possible.
Research from University of Chicago scientists revealed that intermittent fasting can “delay the development of the disorders that lead to death”—meaning that regular practitioners can enjoy a longer, healthier life than people who eat a regular three meals a day or follow a traditional restricted-calorie diet.
A theory on this, according to head of the National Institute on Aging’s neuroscience laboratory Mark Mattson, is that the mild stress intermittent fasting puts on the body provides a constant threat, increasing the body’s powerful cellular defenses against potential molecular damage. Intermittent fasting also stimulates the body to maintain and repair tissues and has anti-aging benefits, keeping every organ and cell functioning effectively and efficiently.
5. Understanding hunger
It’s important to learn how to accurately decipher the signals your body gives you, and intermittent fasting is a great way to understand the cycle of hunger. Before true hunger sets in and the body, if not fed, enters starvation mode, you’ll feel pangs that can generally be attributed to psychological cravings. This emotional desire is often confused with hunger, but fasting will give practitioners the opportunity to experience real hunger pains in the stomach, and even withdrawal and detox symptoms associated with our usual consumption of processed foods.
You’ll also develop a deeper appreciation of food; if you’ve ever eaten after a period of true hunger, you’ll know what eating is supposed to feel like. Each bite tastes more delicious than the last, and you’ll experience a sensation of deep contentment and pleasure. It’s absolutely worth the hunger you endured to get there.
6. Establishes routine
Unless you’re following a random fast type of diet, having strict eating times followed by periods of fasting can help your body develop a solid routine. You’ll be able to recognize your own hunger cycles, you’ll sleep more regularly and soundly, and you’ll start scheduling appointments during convenient hours. It can be difficult to establish this routine at first, especially if you have a family or an inflexible work schedule, but once you’ve developed a consistent plan, you’ll soon start to see all the ways a set routine can benefit your life and your health.
7. Stimulates brain function
A study discussed at a meeting of the Society for Neuroscience in 2015 revealed that intermittent fasting offers “enormous implications for brain health.” According to the study, which was undertaken on both humans and animals, fasting stimulates the brain in a number of different ways: promotes the growth of neurons, aids in recovery following a stroke or other brain injury and enhances memory performance. Not only does intermittent fasting help decrease a practitioner’s risk of developing neurodegenerative diseases like Parkinson’s or Alzheimer’s, evidence shows it may actually even improve both cognitive function and quality of life for people living with those conditions.
8. Boosts immune system
According to scientists at the University of Southern California, fasting has the power to “regenerate the entire immune system” by boosting the body’s production of new white blood cells, which is how your body fights off infection. Fasting in cycles, like practitioners of intermittent fasting will do on a daily or weekly basis, enables your body to purge the damaged, old, or inefficient parts of the immune system, and replace them with newly generated immune system cells.
Studies showed that a 72-hour fast was even enough to help protect cancer patients from the harmful and toxic effects of chemotherapy treatments—which generally causes significant damage to the patient’s immune system. Further clinical trials are needed, but many researchers are confident that intermittent fasting could be incredibly helpful for immunocompromised individuals and the elderly.
9. Rejuvenates skin
Acne sufferers know one of the best ways to control bothersome skin conditions is through diet, eating only unprocessed foods and limiting consumption of dairy products. It’s no surprise, then, that regular intermittent fasting can offer impressive benefits that can be seen on a practitioner’s radiant face. Many of these conditions are caused from food sensitivities, which can lead to inflammatory conditions and acne. After a fast, introduce foods one at a time and note any changes to your skin, to accurately pinpoint which foods should be avoided.
Intermittent fasting also has a positive effect on hair and nails, helping them grow healthy and strong. Not only will you feel good after incorporating intermittent fasting into your lifestyle, you’ll look great, too.
10. Improves spiritual well-being
Fasting is practiced by almost every religion around the world. It’s no surprise that a lifestyle that includes intermittent fasting could lead to a deepened sense of spirituality. Regular practitioners have reported feeling at peace during their fasts, and studies have proven that fasting can help regulate mood by reducing levels of anxiety and stress. In fact, fasting is recommended as a natural treatment for a variety of emotional and sexual problems.
Whether or not you fast for religious reasons, intermittent fasting will help you feel more connected to nature and the world around you, and you’ll benefit from having a clear mind and a positive outlook.
11. Reduces oxidative stress
Oxidative stress is caused by an imbalance in the body’s production of reactive oxygen and its antioxidative defenses, and may lead to chronic diseases and cancers. Unstable molecules, known as free radicals, can react with important molecules like DNA and protein, damaging these molecules and creating an imbalance.
The weight reduction brought on by regular intermittent fasting can lead to a reduction in the body’s level of oxidative stress, helping prevent the development of these unpleasant conditions. A greater antioxidant capability is a huge benefit that comes with intermittent fasting, and one that shouldn’t be overlooked by anyone looking to pursue improved health and well-being.
12. Improves heart function
A lower body fat percentage has wide-reaching benefits through the entire body, but possibly none more important than cardiac function. Consistently, studies have shown that Mormon populations show lower cardiac mortality, generally attributed to the fact that Mormons don’t smoke, drink, or eat large amounts of meat. In addition, Mormons practice intermittent fasting.
Intermittent fasting can lead to a reduction in cholesterol levels—particularly triglycerides, which the body uses to create energy. Having less body fat also takes some strain off the kidneys, lowering blood pressure and increasing the body’s production of growth hormones. Combined, these benefits can mean a significant improvement in heart function.
13. Helps prevent cancer
Intermittent fasting’s impressive ability to stimulate growth hormone production is also important for reducing a practitioner’s risk of developing a number of types of cancer. Regular eating triggers the body to produce more and more new cells—which can inadvertently speed up the growth of certain cancer cells. Fasting, however, gives your body a bit of a rest from this activity, and lessens the possibility of new cells becoming cancerous.
In addition, studies have indicated that when combined with chemotherapy, a “fast-like diet” can help tear down the protection that prevents the immune system from attacking breast cancer and skin cancer cells.
14. Speeds healing and recovery
Exercising while fasting can be tricky, but there are some powerful benefits to be gained by combining the two—especially when you can get a solid workout in at the end of your period of not eating. Some studies have reported that after three weeks of regular overnight fasting, endurance cyclists noted a more rapid post-workout recovery—with no decrease in performance. Studies examining weight training in a fasted state showed an increase to the subject’s “intramyocellular anabolic response” to the post-workout meal, indicating that the period of fasting upped some of the body’s physiological indicators of muscular growth.
Even if these studies aren’t entirely conclusive, the healing power of fasting and the improvements to your sleep and eating habits definitely aids the body in recovering from a workout, no matter how intense it is.
15. Triggers autophagy
During a fast, the body’s cells begin to undertake a process called autophagy. Over time, dysfunctional or damaged proteins can build up within cells, and this waste removal process helps the body filter out this excess material. This process is an important part of the body’s ability to repair and detoxify, and some researchers assert that increased autophagy offers a boost in protection from a number of diseases, including cancer and Alzheimer’s disease.
Autophagy helps cells overcome stresses brought on from external causes like the deprivation of important nutrients, as well as internal issues like pathogens or invading infections organisms.
Can I exercise while fasting?
Since food provides your body with the fuel necessary to get through a tough workout, it is beneficial to exercise during your fast, as long as you do it correctly. Your body generally uses stored carbohydrates in the form of glycogen to power you through your workout. During a fast, when your glycogen reserves are depleted, your body will be forced to turn to other energy sources for fuel—like fat. However, experts recommend that if you’re fasting, keep your workouts short.
“When glycogen is in short supply, your body also reverts to breaking down protein—your muscles’ building blocks—for fuel,” said Kelly Pritchett, an assistant professor in nutrition and exercise science at Central Washington University.
This means even though you will likely burn more fat if you’re exercising on an empty stomach, you could also start burning protein if you work out too hard without fueling your body with carbs, leading to a loss of muscle mass, in addition to fat.
Without food, you’ll also feel the weakening effects of lowered levels of glycogen and blood sugar. As your body adjusts to regular intermittent fasting, you’ll be able to handle this energy loss a bit better, but initially, overdoing it with your workouts could be detrimental. Make sure you’re getting enough rest to compensate for your lowered energy level before you attempt to get on the bike or start pounding the pavement.
Challenges to expect during a fast
Fasting can be a difficult practice to incorporate into a busy lifestyle, especially for individuals who have never monitored meals or counted calories in the past. For people who are newly adopting a healthy diet and exercise program, it’s a good idea to develop a routine and let your body adjust before attempting to bring in an intermittent fast plan.
Working your scheduled fast periods around your family, job and other commitments can also be a struggle. If you have the support of your workplace and your loved ones as you incorporate fasting into your life, it will be a lot easier to stick to your eating routine. Since you will likely face a brief period of lowered energy and some mood swings initially, it can be beneficial to arrange for your first fasts to fall on weekends, or days with less scheduled activity. Be prepared to feel a bit rundown as your body adjusts to a new eating schedule.
People who have struggled with eating disorders in the past can find fasting may trigger relapses—particularly binge eaters. The hunger that can develop during a period of fasting could lead you to overeat during your feeding days, but this is generally not a problem for people who have a healthy attitude toward food and eating. If you’ve experienced food-related mental health issues, a diet that incorporates any period of fasting for longer than eight to 12 hours might not be appropriate.
Finally, fasting is generally not a good idea if you’re pregnant. When your body is growing another human inside it, you’ll need to fuel it frequently and make sure you’re getting all the nutrients you need in regular doses; however, there is no research to show that fasting is a harmful practice for pregnant women. Some Muslim women do choose to practice fasting during Ramadan even throughout a pregnancy, but all pregnant women are encouraged to discuss drastic dietary changes with their doctor to ensure it will be safe for the baby.