Fasting, a period of not eating, is the single most effective (and underrated) thing that you can do to lose weight. It’s completely obvious when you think about it, but you don’t hear about it often. It’s usually only mentioned in religious contexts.

When you’re fasting, you’re using your stored resources (carbs and fats) to their full potential because that’s the only energy available to you. It’s the single most effective way to lose body fat.

The reason that people don’t do it (or even consider it)? They think that fasting is dangerous.

If you don’t know, let me be the first to break it to you: you don’t have to eat every day. You don’t even have to eat for a month if your body has enough stored fat. One guy even made it over a year without eating because he had enough stored fat.

It’s completely healthy to fast. You won’t die, and you won’t be completely exhausted.

Here’s my five-sentence thesis on why fasting is healthy and natural:

Why do you think we’re so good at accumulating fat stores? Years ago our ancestors didn’t know where their next meal was coming from, so when they were able to feast, they feasted like crazy. Excess energy was stored as fat. You could have a period of weeks before you found your next large food source, so energy storage was crucial for our primitive survival. We still have this capability today, but no longer exercise it.

The only downside to fasting? It can be difficult. After a lifetime of eating 3 meals a day, it’s mentally challenging to recondition yourself to eat less often. You’ll want to eat when you’re used to eating or when you’re bored. You may also grow fatigued more easily.

Thankfully, you don’t have to do multi-day fasting to get most of the weight loss benefits. There are some easier forms of fasting that are also very effective.

But before I mention the different types of fasting…

Most Important: Your Health

DISCLAIMER: I’m not a doctor, and none of this information is intended as medical advice. I encourage you to use this info however you’d like and make your own informed decisions at your own risk. If you’re concerned about how fasting may affect your health, you can always try it for a short period, and if you decide it’s not right for you, no harm done.

As with any type of large lifestyle change, there are some precautions that you should take before you begin fasting, especially if you opt for water fasting.

Consider your age and overall health. If you’re old and/or sick, I don’t recommend that you fast.

Make smart decisions. For example, don’t jump straight into water fasting if you’ve never eaten less than one meal a day.

Many doctors will not support your decision to fast. It’s not well studied, and it’s certainly not mainstream advice. If you want medical supervision, get it from an open-minded doctor who will support your choices and take care of you.

Water fasting is dangerous if done improperly. See the warnings under the “Water Fasting” section.

Use some common sense if you attempt fasting. Listen to your body. Some of the hunger that you’ll feel is “fake” from your conditioning, but if something feels wrong, break your fast with a small, wholesome meal, and try again some other time.

Intermittent Fasting

Intermittent fasting describes any form of fasting that involves eating during a restricted time window. When you eat all of the time, your body prefers to use the incoming energy from food (particularly carbohydrates), so by limiting that time period, your body will use more of your stored energy.

Here are some concrete examples of intermittent fasting. You can use any of these as-is, or use them as a guide to make your own fasting plan:

  • Only eat between 12pm-8pm each day (also known as 16:8; I recommend this one)
  • Eat one large meal a day at the same time
  • Don’t eat anything between bedtime and lunch
  • Only eat one meal every two or three days

People tend to overcomplicate intermittent fasting with lots of rules, variations, and plans, but it’s really easy. Pick something that works for you mentally, and stick with it.

This is a powerful, personally maintainable, and flexible strategy. You don’t have to give up eating, just eating at specific times of day.

I recommend that you use intermittent fasting with the ketogenic diet for an effective, maintainable weight loss plan. The two will complement each other and accelerate your weight loss.

Water Fasting

Also known as fasting. When you’re water fasting, you’re only drinking water, black coffee, tea, and maybe diet soft drinks. You’re eating absolutely nothing.

The idea is incredibly simple, but it’s mentally challenging. The longest I’ve ever fasted was six days. It was a difficult experiment, but I used work and other things to distract myself from wanting to eat when I was bored.

I was already fairly low body fat when I tried water fasting for the first time. I imagine that the more weight you’re carrying, the easier it will be mentally since your body is aware that you have more energy available.

If you want to try long-term fasting, use longer periods of intermittent fasting to segue into it. I do not recommend that you start water fasting cold turkey, but if you choose to, be cautious.

There are two critically important rules you must follow for your safety:

  • Do not drink excessive amounts of water or allowed beverages as doing so will flush and deplete your electrolytes (which is dangerous for your heart).
  • Do not eat very low calorie meals to curb your hunger, especially frequent ones. If you choose to fast, stick with it. You’ll damage your metabolism at best and starve yourself at worst.

And some good advice:

  • Keep vitamins and electrolytes on hand if you’re new to water fasting. If you feel low-energy, try taking them. Just be aware that there are some vitamins (like zinc, for example) that you should avoid taking with an empty stomach.
  • Water fast under doctor supervision if you want to try it but have personal health concerns or some type of pre-existing condition.

Additional Health Benefits

This site is intended as a weight loss guide, so I won’t go into great detail about other benefits of fasting, but it’s been shown to improve your health in other ways. There’s plenty of info online, so Google these things if you’re interested. If you want tons of information quickly, Dr. Jason Fung has the most comprehensive water fasting resource online.

Water fasting has been shown to reverse type 2 diabetes, high cholesterol and triglycerides, and metabolic syndrome. This is because your body gets a break from dealing with sugar, insulin, free radicals, and other stressors. During this period, it will repair itself.

After about 3 days of water fasting, your body begins performing autophagy, a process where undesirable proteins are broken down and used to rebuild other tissue. It’s still a fairly new research topic, so it’s tough to say how beneficial it is for your health.

That’s it for fasting. It’s pretty simple, and you can customize it however you like as long as your fasting periods exceed 12 hours.

Next, for the sake of completion, I’ll describe a modified form of fasting that will give you most of the speed of water fasting, but will still allow you to eat one or two meals a day. With some caveats.