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What Is Intermittent Fasting? What Are the Different Types?

Intermittent fasting involves eating for a certain period of time (eating window) and then not eating for a certain period of time (fasting window). Here are the different types:

  • 12:12: You eat for 12 hours of the day and fast for the other 12. For example you'd eat from 7:00 a.m. until 7:00 p.m. every day. This is perfect for IF newbies as it's consistent every day, you can eat three regular-timed meals, and it can help those who tend to overindulge with bedtime snacks.
  • 16:8 or Leangains: Probably the most popular form of IF, you eat eight hours of the day and fast for 16. An example would be eating from noon until 8 p.m., basically just skipping breakfast. This is something you can do every day, and still be able to enjoy dinner with the family or out with friends. If you're a morning eater, you can eat from 8 a.m. until 4 p.m. — you can make the eight-hour eating window work for you.
  • 5:2 or Fast Diet: Twice a week (nonconsecutive days) you restrict calories to around 500 calories a day (600 calories for men), and on the other five days, you eat as if you are not on a diet. On the fasting days, you can eat three small meals or two slightly larger meals (lunch and dinner).
  • Eat, Stop, Eat: Once or twice a week, you fast for 24 hours — you never go a day without eating. Eat dinner Monday night, finishing by 7:00 p.m., fast all day Tuesday, then eat dinner at 7:00 p.m. on Tuesday night. Choose the one or two days that work with your schedule. This might be a good option if you've tried 16:8 or 5:2 and have hit a plateau.
  • Alternate Day Fasting: You fast one day (or in a modified version, eat up to 500 calories that day), then eat normally the next day, and repeat. You essentially fast every other day. Alternate-day fasting might be a good plan if it fits your lifestyle, if you have a lot of weight to lose and want to see quicker results, or if you've tried 16:8 or 5:2 and have hit a weight-loss plateau.
  • 20:4 or Warrior Diet: You fast for 20 hours out of the day, then have a four-hour eating window. An example would be eating from 2:00 p.m. until 6:00 p.m. This is an advanced method of IF, but some people with busy schedules or issues with eating all day prefer this method.
Image Source: Getty / martin-dm