One of the oldest and most familiar ways lose weight is simple calorie restriction — so if we take that to the extreme, fasting to lose weight should be the fast-est (see what I did there?) way to shed those pounds, right? In theory, yes; for all you efficiency freaks out there, taking in zero calories would be the fastest way to lose weight, but serious health risks are involved with such a stunt. As with most things in life, moderation is key, and a much safer and easier way to fast to lose weight is the more moderate intermittent fasting.

What is intermittent fasting?

Intermittent fasting is an eating schedule that involves alternating between periods of eating and fasting. This period of fasting can be anything, from hours (e.g. dinner to breakfast) to even days. Intermittent fasting has actually been practiced for millennia — though not always by choice — as our ancient ancestors didn't always have a consistent food supply and frequently had to experience periods of restricted caloric intake. In this way, intermittent fasting is similar to the paleo diet, which tries to mimic the diet of the earliest humans.

Some of the most popular intermittent fasting methods are:

• The 16:8: Involves fasting for 16 hours a day and restricting your eating window to only eight hours, for example skipping breakfast and only eating from 2 to 10PM. Several high-profile celebrities swear by this method, from Terry Crews to Hugh Jackman.
• The 5:2: On this regimen, eat as you normally would five days a week, then restrict your calorie consumption to no more than 500-600 calories for the other two days.
• The Warrior Diet: A more extreme version of the 16/8, this method extends the fast to 20 hours, making the eating period just four hours. This essentially means binge eating for four hours a day, or even just eating one gigantic meal a day.

How does fasting to lose weight work?

On a surface level, fasting by definition means you take in fewer calories, and fewer calories translates to less weight gain. 16:8 intermittent fasting has also proved to decrease appetite and boost metabolism, all great traits if you're trying lose a few pounds. Fasting also affects your hormones in a way that is conducive to weight loss. For example, human growth hormone secretion increases, which studies have shown can help you lose weight and build muscle, especially as you age. Fasting also does wonders for your insulin sensitivity; insulin is what causes your body to store excess calories as fat, and insulin levels rise when you eat. The longer you abstain from eating, the more time your body has to lower its insulin levels, which in turn makes it easier to burn off stored fat.

Is fasting to lose weight right for you?

Intermittent fasting can be a very effective weight loss tool — but it isn't for everyone. Most notably, there is evidence that fasting may have the opposite effect on insulin in women than in men. It may also be too difficult or take too long for some people to grow accustomed to an intermittent fasting schedule, especially those who aren't used to going hungry. Eating on a strict schedule can potentially affect your social life as well — imagine not being able to go out for Sunday brunch with your friends or having to pass on grabbing a drink from the local bar after work.

For the reasons listed above, intermittent fasting has often been described as one of the hardest diets to stay on long-term. And when it comes to weight loss, long-term consistency is one of the, if not the most important thing to keep in mind. If the cons of fasting seem too daunting to you, it may be a better idea to just stick with a more traditional calorie-restricted diet.