Updated: Mar 25, 2022
The most accurate definition is the simplest one: IF (Intermittent Fasting) is alternating intervals of not eating (fasting period) with times where you are allowed to eat (feeding period). How long each window lasts depends on the method that you choose to use, and there are several ways you can implement IF into your lifestyle. That is the beauty of it, and why it works so well.
Each option has its benefits, and the choice really depends on your personal preference and #lifestyle. In general, each plan is about 16-36 hours with several stops in between, and each strategy offers its own unique benefits.
Alternate Day Fasting
With this plan, you simply eat every other day. So on Monday, you'd eat within a 12-hour window, say 8 am to 8 pm. Then you'd fast overnight on Monday and all day/ overnight on Tuesday. You'd wat again from 8 am to 8 pm on Wednesday, and so on. Alternate day fasters are aged to make good eating choices, but they're allowed to eat what they want on the non-fasting days.
Some IF proponents believe we should behave as our evolutionary ancestors did. As humans evolved to get their food and exercise randomly, so should we. This brand of IF includes eating unprocessed "evolutionary friendly" food (think Paleo-diet type), randomly cycling daily calorie intake, and randomly skipping a #breakfast or #dinner meal once or twice a week. The rules are very flexible.
Eat Stop Eat
On this plan, you fast for a full 24 hours once or twice per week, eating sensibly (higher #protein, minimizing processed foods, etc.) the rest of the week. It's flexible: You can choose whichever 24 hours you want. Want to fast from breakfast to breakfast? That's cool. Just eat breakfast on Monday, and don't eat again until breakfast on Tuesday.
On this plan, you fast for 20 hours each day, working out during your fasted state. Then, eat your daily food intake within the 4- hour feeding window. After that 4- hour feeding period, fast again for 20 hours. Generally, most people place their 4- hour feeding window at the end of the day, as it's more convenient for family dinners and after-work training sessions. However, 20 hours of fasting and 4 hours of feeding can occur at any time during the day.
Please don't think of IF as some fad diet, crazy #fasting experiment, or a quick fix to lose weight. Instead, think of it as a way to improve appetite control, a proper way to restrict #calories, improve daily production, improve your glucose/sugar #metabolism, increase fat oxidation, improve growth hormone production to burn fat, control hunger, and eliminate waste from the body.
As always, consult with a qualified professional to see if a particular dietary plan is right for you.