Intermittent fasting (IF) is currently one of the world’s most popular health and fitness trends. People are using it to lose weight, improve their health and simplify their lifestyles.

This is the ultimate beginner’s guide to intermittent fasting.

What Is Intermittent Fasting (IF)?

Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating. It doesn’t specify which foods you should eat but rather when you should eat them. In this respect, it’s not a diet in the conventional sense but more accurately described as an eating pattern.

Common intermittent fasting methods involve daily 16-hour fasts or fasting for 24 hours, twice per week.

Fasting has been a practice throughout human evolution. Ancient hunter-gatherers didn’t have supermarkets, refrigerators, or food available year-round. Sometimes they couldn’t find anything to eat. As a result, humans evolved to be able to function without food for extended periods of time.

In fact, fasting from time to time is more natural than always eating 3–4 (or more) meals per day.

Fasting is also often done for religious or spiritual reasons.

Intermittent Fasting Methods

There are several different ways of doing intermittent fasting — all of which involve splitting the day or week into eating and fasting periods. During the fasting periods, you eat either very little or nothing at all. These are the most popular methods:

The 16/8 method: Also called the Leangains protocol, it involves skipping breakfast and restricting your daily eating period to 8 hours, such as 1–9 p.m. Then you fast for 16 hours in between. Many people find the 16/8 method to be the simplest, most sustainable, and easiest to stick to. It’s also the most popular.

Eat-Stop-Eat: This involves fasting for 24 hours, once or twice a week, for example by not eating from dinner one day until dinner the next day.

The 5:2 diet: With this method, you consume only 500–600 calories on two nonconsecutive days of the week, but eat normally the other 5 days.

By reducing your calorie intake, all these methods should cause weight loss if you don’t compensate by eating much more during the eating periods. Keep in mind that the main reason for its success is that intermittent fasting helps you eat fewer calories overall. If you binge and eat massive amounts during your eating periods, you may not lose any weight at all. Additionally, intermittent fasting changes hormone levels to facilitate weight loss.

By helping you eat fewer and burn more calories, intermittent fasting causes weight loss by changing both sides of the calorie equation. Studies show that intermittent fasting can be a very powerful weight loss tool that switches your body from burning glucose to burning fat.  Fat is simply the body’s stored food energy. In times of low food availability, stored food is naturally released to fill the void. The body does not “burn muscle” to feed itself until all the fat stores are used up.

A 2014 review study found that this eating pattern can cause 3–8% weight loss over 3–24 weeks, which is a significant amount, compared to most weight loss studies. People also lost 4–7% of their waist circumference, indicating a significant loss of harmful belly fat that builds up around your organs and causes disease.

Health Benefits

Many studies have been done on intermittent fasting, in both animals and humans. These studies have shown that it can have powerful benefits for weight control and the health of your body and brain. It may even help you live longer.

Here are the main health benefits of intermittent fasting:

Weight loss: Intermittent fasting can help you lose weight and belly fat.

Insulin resistance: Intermittent fasting can reduce insulin resistance, lowering blood sugar by 3–6% and fasting insulin levels by 20–31%, which should protect against type 2 diabetes.

Heart health: Intermittent fasting may reduce “bad” LDL cholesterol, blood triglycerides, inflammatory markers, blood sugar and insulin resistance — all risk factors for heart disease.

Brain health: Intermittent fasting increases the brain hormone BDNF and may aid the growth of new nerve cells. It may also protect against Alzheimer’s disease.

Anti-aging: Intermittent fasting can extend lifespan in rats. Studies showed that fasted rats lived 36–83% longer.

Makes Your Healthy Lifestyle Simpler

One of the main obstacles to eating healthy is all the work needed to plan for and cook multiple healthy meals in a day. Intermittent fasting can make things easier, as you don’t need to plan, cook, or clean up after as many meals as before. For this reason, intermittent fasting is extremely popular among the life-hacking crowd, as it improves your health while simplifying your life at the same time.

It is important to eat healthy during the times you are not fasting. The following rules are important to follow:

• Eat whole, unprocessed food
• Reduce sugar and refined grains
• Eat more natural fats
• Eat less artificial fats

Safety and Side Effects

Hunger is the main side effect of intermittent fasting. You may also feel weak, and your brain may not perform as well as you’re used to. This may only be temporary, as it can take some time for your body to adapt to the new meal schedule.

If you have a medical condition, you should consult with your doctor before trying intermittent fasting.

Intermittent fasting is certainly not for everyone. This is particularly important if you:

• Have diabetes.
• Have problems with blood sugar regulation.
• Have low blood pressure.
• Take medications.
• Are underweight.
• Have a history of eating disorders.
• Are a woman who is trying to conceive.
• Are a woman with a history of amenorrhea.
• Are pregnant or breastfeeding.

Intermittent fasting has an outstanding safety profile. There is nothing dangerous about not eating for a while if you’re healthy and well-nourished overall.

“The Complete Guide to Fasting – Heal Your Body Through Intermittent, Alternative-Day, and Extended Fasting” by Jason Fung, MD with Jimmy Moore is an excellent resource to learn more about this fascinating topic. It is available on Amazon.

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