Fasting is one of the oldest diet methods in the world—it dates as far back as the 5th Century BCE, when it was recommended by the Greek physician Hippocrates as a means of combatting symptoms of a number of illnesses .
Modern research into fasting has proven Hippocrates had the right of it. Fasting triggers autophagy, the internal process through which your body recycles “cellular junk” into new, healthy, and highly functioning cells.
For those who are trying to age gracefully, improve their health, and manage their eating habits, fasting has the potential to be a truly effective option.
But what is fasting, really? How does it work? Are you supposed to go for days without eating or drinking anything? And if so, for how long?
That’s what we’ll answer in this blog post!
Below, we’ll talk about the various types of fasting, and offer some recommendations that will help you incorporate it into your specific lifestyle.
Research into fasting is still very much in its infancy. There’s so much yet to discover about fasting and its effects on your body.
However, based on what is already widely known , fasting has the potential to provide some pretty amazing benefits:
Improved working and verbal memory
Increased fat loss, but without the muscle mass loss often accompanying fat loss
Reduced tissue damage following injuries and surgeries, as well as faster recovery rates
Improved heart health, including lower heart rate and lower resting blood pressure
Decreased rates of Type 2 Diabetes and obesity
Lower risk of Crohn’s disease, Parkinson’s, Huntingdon’s, kidney disease, liver disease, and even cancer
As with any calorie-restricted diet, there are some dangers to be aware of.
Children or teenagers under the age of 18 should not fast. Their bodies are still growing and need a steady supply of calories in order to properly develop.
Pregnant women or breastfeeding mothers also should avoid fasting, because it could have unknown detrimental effects on the growing fetus or their nursing infant.
People with a history of eating disorders are also recommended to steer clear.
People with Type I Diabetes who take insulin may also want to avoid fasting. Fasting may lead to critically low blood sugar levels (a problem for those with this diabetes) and thus may prove dangerous.
However, if done correctly (read: safely) fasting has the potential to offer all the benefits with none of the risks or side effects listed here.
Before you dive into fasting, it’s important to understand the various types of fasting, as that will help you decide which will best serve you and your specific lifestyle.
Here are the primary methods of fasting backed by research :
Intermittent Fasting. Also called “time restricted fasting”, intermittent fasting involves eating all of your calories during a specific time period (usually 6 to 8 hours), then fasting during the remaining hours of the day (16 to 18 hours). During the “fast” periods, you consume no calories, only water or coffee and tea with no milk or sugar added.
Alternate Day Fasting. This fasting regimen involves 24 hours of eating as normal (regular amounts of calories) followed by 24 hours of fasting. Typically, during the “fasting” days, you consume around 500 to 800 calories—just enough to keep your body functioning while still restricting caloric intake.
Periodic Fasting. This plan calls for extended periods of fasting (usually 24 to 72 hours) . An example of a periodic fasting diet would be the 5:2 Diet, which is 5 days of eating normally followed by 48 hours of restricted calorie intake (usually 500 to 600 calories). Strict fasting diets should not last longer than 72 hours. The primary benefits are believed to occur within the first 24 to 48 hours, but fasting for longer than 72 hours is much more challenging on your body and should only be undertaken under the strict supervision of a medical professional.
Fasting-Mimicking Diet. This isn’t exactly a fasting diet, but one that mimics the effects of fasting. For 48 hours, you consume normal calories, then spend the next five days consuming around 700 to 1100 calories of primarily “healthy” unsaturated fats in order to trigger ketosis. Research  indicates that this diet has the potential for the same long-term health benefits that “proper” fasting does, in everything from slowed biological aging to reduced disease to increased longevity.
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The type of fasting diet to try will depend largely on your lifestyle.
People who work at manual labor and jobs that require a great deal of intensive activity may want to try intermittent fasting. That way, they get enough calories in their day to maintain the necessary energy expenditure, but still limit their food intake during their “off hours”.
People who work at office jobs may find that intermittent fasting is easier, too. Your first meal is eaten after you arrive at the office, and the last meal is eating just before leaving. In the morning and evening, you consume zero-calorie beverages (water, tea, coffee, etc.) but eat all your calories over the course of your work day.
However, people who work more sedentary jobs (white collar, for example) may find that periodic fasting is a possibility. Sure, it’s difficult to avoid temptation when there are donuts in the break room or everyone goes out for drinks after work., But you can structure your fast in a way that you won’t miss out on social events and rely on your willpower to keep you from eating snack foods during your fasting period.
People who work from home or who are stay-at-home parents may be able to consider longer fasts, as they are doing so from the comfort of their house and have easy access to healthy food and their kitchen throughout the day. They can cook up a simple, low-calorie meal as needed and as their hunger demands. They’re also only cooking and eating what’s available in their home, so it’s easier to shop smart and stock your shelves and fridge with only the healthy, natural, and low-calorie foods you’ll be eating during your prolonged fasting days.
The most important thing to remember when fasting is that you need to listen to your body.
Your body will respond strongly when you first start fasting. After all, it’s accustomed to a certain caloric intake, so depriving it of nutrients may cause negative reactions : headaches, lethargy, irritability, and even nausea.
But those symptoms will usually decrease over time and with repeated fasts (whether intermittent or periodic). Or, you’ll grow accustomed to those symptoms as a “normal” part of the fast.
You still need to be on the lookout for other less “normal” or healthy symptoms, including slowed metabolism, excessive appetite, more frequent instances of binge-eating following your fast, extreme sluggishness and low energy levels, low blood pressure, and low blood sugar.
These are signs that A) you’re fasting too long, B) you’re being too strict with the calorie intake, or C) you’re fasting too frequently.
Listen to your body and pay attention to what it demands of you. If you need more food to function normally throughout your busy day, eat a bit more, or drop the fast altogether. Only continue fasting if you’re feeling good. Too much “struggle” can actually be a sign your body is responding poorly to the calorie-restricted diet.
At the end of the day, being safe and smart is the key to effective fasting. Done right, it can have huge benefits for your body (as you saw above) without any significant downsides. You’ll find yourself feeling better and living longer thanks to the positive effects of healthy fasting.
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