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20 Facts About Fasting (Backed By Science)

by | Jul 16, 2020 | FAST FACTS

1. The longest fast on record lasted for over a year – 

In 1973, a morbidly obese man by the name of Angus Barbieri completed a fast of 382 days – the world’s longest (and arguably most effective) fast on record. During that year, Barbieri, who started at 456 pounds, achieved a final weight of 180. That’s a total loss of 276 pounds. Barbieri’s fast was medically supervised, and he consumed zero-calorie liquids such as coffee, tea, electrolyte water, and sparkling water. Study authors concluded that prolonged fasting had “no negative effects on the patient.”

2. Fasting decreases your biological age

So there’s your chronological age, which is how many times you’ve circled the sun, and there’s your biological age – how old you are based on the health of your cells. Many habits such as smoking, overeating, drinking too much alcohol and living a sedentary life increase your biological age. (A thirty-year-old might have a biological age closer to fifty, in this instance.)

But the habit of fasting reduces your biological age via the process of autophagy, which rejuvenates your cells and repairs damaged DNA. A seventy-year-old who fasts regularly could have a biological age closer to thirty!

3. Your weight will bounce back up a little after a fast – and that’s okay

It might seem sad when you’ve lost six pounds after a two-day fast only to gain two a third of the weight back the next day. But this minor rebound is entirely normal – and you’re not regaining fat! Your body is merely adding back the water weight that you lost when you were fasting. And if you can anticipate this next time you fast, you won’t be psychologically devastated (or maybe just miffed) when you your weight jump up a skosh.

Pro-tip: unless you’re doing prolonged fasts where your weight needs to be monitored for health reasons, try to focus more on the process of regular fasting than on the scale.

4. Fasting increases NAD – the longevity chemical

For those of you who don’t know what NAD is (also known as NAD+), it’s a coenzyme that’s important for metabolic health, aging, DNA repair, and energy production. It’s also being sold as pills and IV therapy that cost a ton of money. But research shows that fasting significantly boosts NAD levels – and you don’t have to spend a dime!

5. Despite 70 years of research, fasting is NOT taught to doctors in med school

We’re not drumming up conspiracies here, but America fares worst among industrialized nations for health while spending the most on healthcare. That’s a fact. This is because doctors are paid to prescribe pharmaceuticals for diseases like obesity, diabetes, and CVD, and they completely ignore the free treatment of fasting (even though it has 70+ years of research behind it). Doctors simply have no med-school education in the subject of fasting for health.

Thankfully there are doctors such as Mark Hyman, David Perlmutter, and Dan Pompa, who are helping to increase medical awareness of fasting.

6. Fasting is actually a stress to the body

Fasting achieves its many benefits not by resting the body, but by stressing the body. The mild stress of fasting (known as hormetic stress) sparks a cascade of hormones that stimulate autophagy, weight loss, and metabolic healing. Other hormetic stressors include exercise, heat exposure, and cold exposure, which are often used alongside fasting for increased results.

7. Several fasts allow you to eat

Fasting and eating is like day and night, or hot and cold – polar opposites, right? That’s what everyone who’s just learning about fasting thinks. But actually, some of the most scientifically validated forms of fasting (such as the Fasting Mimicking Diet and alternate-day fasting) involve chowing down on small portions of food. These ‘food fasts’ have been demonstrated to be just as effective as regular fasting in most areas, and even more beneficial in other areas such as gut health.

Don't know which fast is right for you? Read this article


8. Everyone fasts

Being honest, fasting can seem pretty scary at first. We’ve been conditioned to eat at least three times per day since childhood, and our brains are so used to the constant influx of protein, fat, and carbs that we shudder at the idea of going without. But in reality, you fast every – single – night. Your body’s insulin levels drop in the evening, which signals your body to start burning fat instead of storing it. (This is why you can sleep without dying of starvation.)

The only difference between fasting while asleep and awake is that we’re psychologically conditioned to crave food all day because that’s what we always do. But if you resist that first wave of hunger, your insulin levels will stay low, and your body will continue to burn fat for fuel. The more you practice this, the better (and thinner) you get.

9. Fasting can help you sleep better

You know how when you eat too late, it’s hard to fall asleep? This isn’t just indigestion. The process of digesting food signals to your body’s circadian clocks that it’s time to be awake – which then tells your brain to be alert. But when you fast practice the fasting method of time-restricted eating (TRE), which is eating all of your food in the morning and afternoon, never at night, your body falls back to its natural circadian rhythm, which leads to better sleep.

Scientists say that many participants who started TRE continued this fasting method for sleep improvements!

10. You won’t die if you dry fast

As if normal fasting weren’t hard enough to wrap your head around, there’s dry fasting: abstaining from food and water. Why would anyone do that, you ask? Well, dry fasting is thought to harness the benefits of autophagy and fat burning quicker than a standard fast. (Some experts say that one day of dry fasting is equivalent to three days regular fasting.)

This could be due to the body breaking down damaged cells more quickly in search of inner water, and the body burning fat to increase the production of metabolic water. Since there haven’t been many studies conducted on the mechanisms of a dry fast, the jury is still out. But in a study of participants dry fasting for five days, there were no adverse effects reported – not even dehydration!

Dry fasting is still considered the riskiest form of fasting, and should not be done for longer than a day without medical supervision.

11. Coffee is 100% allowed on a fast – and it’s beneficial, too

People have this idea that fasting means ‘total deprivation’. Nope. Creature comforts like coffee, tea, and sparkling water are totally kosher with most fasting methods. In fact, coffee is known to accelerate autophagy, which is one of the main benefits of fasting. And it does this without significantly elevating insulin levels or blood glucose – two indicators of the fasting state.

So cheers to starting your next fast with a cup of your favorite coffee or tea! Just make sure that you’re not adding calories to your beverages. (Zero-calorie sweeteners like stevia and monk fruit powder are allowed. Just steer clear of fillers like maltodextrin, which can bump up your insulin levels.)

12. Fasting is different for men and women

Fasting is not the same for everyone. Women generally store more fat than me and have lower blood sugar levels, which can lead to more hunger and discomfort during a fast than men experience. Though there is very scant research on fasting and women, studies on mice indicate that females are more prone to emaciation and hormonal imbalance than men when fasting.

Women should follow these tips when starting a fasting regimen:

» try not to fast in your luteal phase, when hunger cravings and mood swings are at their height
» if you have low body fat, don’t fast more than 12 hours a day regularly: it may interfere with your hormones and even disrupt your menstrual cycle
» if longer fasts are painful, try the Fasting Mimicking Diet, which allows around 500-600 calories per day

13. Fasting is helping people to beat cancer

Studies show that fasting enhances chemotherapy treatment while protecting healthy cells. Researchers believe this anti-cancer effect is at least partially caused by reduced levels of insulin growth-like factor 1 (IGF-1), a hormone that’s associated with inflammation and decreased longevity. Combined with high doses of vitamin C, fasting has also shown promise in treating certain forms of cancer.

14. Fasting is the oldest known health remedy

Practitioners have used fasting as a medical treatment for at least 2,500 years. Hippocrates, the father of modern medicine, used fasting to help patients’ bodies recover naturally from various ailments. He is popularly quoted as saying, “To eat when you’re sick is to feed your sickness.” Paracelsus, another famous healer, said that fasting “is the great healer within.”

These early physicians didn’t know about the process of cellular autophagy, which is recognized today as being a main healing component of fasting. But they certainly could see the end result of fasting – which is better health!

Even though fasting has been a safe and effective therapy for thousands of years, it’s still important to consult with your doctor before attempting any fasting protocol. You can learn more about each fasting method here.

15. Fasting can be an essential part of your beauty regimen

No, we’re not talking about starving yourself to achieve the fashion industry’s unrealistic, photo-shopped ‘ideal’ of a beautiful body – fasting has been proven to enhance skin quality. Many beauty experts have recommended fasting for glowing, youthful skin. And studies show that various types of fasting affect skin in different ways, from the easement of acne, to faster wound healing.

You have to make sure to eat a well-balanced diet, though. (No starving yourself!) This is because fasting initially decreases levels of collagen – the protein that makes your skin firm and plump – and it only rebounds to higher levels once you’ve broken the fast with nhealthyeating. This is especially true if you’re consuming high-collagen foods such as bone broth, stews, and gelatin.

16. You could become more productive through intermittent fasting

Eating 10-20 times per day (as most of us do considering snacks and meals) is a bad idea for your health for the same reason that it’s terrible for your productivity. See, every time you eat, your body has a spike of blood glucose that halts restorative processes within the body while telling your body to store food as fat. This same spike in blood sugar leads to decreased focus and cognitive ability – which could negatively impact your work.

While intermittent fasting, your blood sugar, and insulin levels remain neutral for your whole fasting window. And if you’re fasting from 7:00 pm to 11:00 am every workday, that means you have an entire morning of high focus practically without the constant distraction of eating! Many high performers in the world of entrepreneurship and business swear by the intermittent fasting routines.

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17. You can (and should!) be active when you fast

Fasting is a time of rest and rejuvenation, for sure. But think of our ancestors: they routinely went weeks in between meals, yet they had to walk long distances, search for their meals, and sometimes even make a mad dash away from the proverbial bear. This amounted to quite a bit of mild to moderate exercise with no (or nearly no) food!

Bottom line: you definitely don’t have to be a bump on a log when you’re fasting. Here are three great reasons to be active when you fast – 

» Studies show that fasted exercise is a great way to enhance fat burning. (Aim for mild aerobics and weight training – especially during intermittent fasts.)

» Since fasting is a cleansing process, walking and light exercise is a great way to help with lymph flow and detox during prolonged fasts

» Exercise is a known hormetic stressor. Combined with fasting, exercise can increase the upregulation of DNA related to longevity and health.

18. Fasting can make you less hungry

You’d think that going long periods without food would make you so ravenously hungry that you could conceivably eat tree bark. But some research shows that’s exactly the opposite of what really happens. In a study done on 11 overweight adults over four days, appetite regulation was enhanced through a time-restricted eating schedule.

This doesn’t mean that you won’t occasionally get hungry while fasting, or have to deal with hunger in your first few fasts. (You will!) But it shows that your body – or more likely, your brain – responds to new eating habits in adaptive ways that support your long-term fasting goals.

If you’re having trouble with hunger pangs during your first few fasts, try drinking a tablespoon of apple cider vinegar in 12 oz of water. This won’t break your fast, and it’ll help with ketone production and satiety!

19. It’s super important to stay hydrated on a fast

Did you know that up to 30% of your daily hydration comes from the food you eat? It’s true – many of the foods we consume contain high proportions of structured water that hydrates us every bit as much as drinking water. (Some argue that food is even better at hydrating than water!)

To make up for this hydration deficit, it’s essential to consume more liquids than usual on a fast (and especially on prolonged fasts). But beware: drinking too much plain water can dilute the electrolytes in your blood and cause energy dips, headaches, and even heart palpitations. That’s why experts suggest taking a pinch of sea salt with every glass of water on your fasting days. 

Be sure to consult your doctor before fasting. He or she may have you supplement with electrolytes such as potassium, sodium, and magnesium while you fast.

20. It’s possible to achieve peak performance through fasting

We know…with all the headaches and fatigue that can happen in your first fast, and this one is kind of hard to believe. But evolutionary scientists contend that our ancestors’ mental and physical performance did increase while fasting because if it decreased, early man wouldn’t have been able to get their next meal when they needed it most. This is backed up by research that shows an increase in cognitive abilities while fasting.

About The Author

Fast Times Editors

Your go-to-crew for all things fasting and lifestyle. Fasting.com is digital destination for the latest science, strategies, solutions and stories to help the public discover and uncover the benefits of fasting, answer all of their fasting questions and find the best next step and resource to get started.

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