Intermittent fasting may be the most popular diet for the 21st century. It requires eating schedules that flex between fasting and non-fasting over a period of time.

According to MedicalNewsToday.com, there are seven ways to do intermittent fasting:

1. Fast for 12 hours a day, which can include sleep time.
2. Fast for 14 or 16 hours a day. This method, known as the Leangains diet, has different time frames for women and men respectively.
3. Fasting for two days a week. While it is not a true fast on those two days, it is a minimized amount of food intake, about 500 calories for women and 600 calories for men to maintain energy.
4. Alternate day fasting, again with minimal amounts on fast days but unlimited amounts on non-fast days.
5. A weekly 24-hour fast, commonly referred to as the Eat-Stop-Eat diet, with no food eaten on the fast day.
6. Meal skipping, which is one way to start training for a longer fast.
7. The Warrior Diet, which leaves open a 4-hour window daily for food intake, one large meal, while the other 20-hours can be sustained by a few servings of raw fruits or vegetables.

Some dieticians believe that intermittent fasting can reduce the risk of diet-related diseases, while others see it as just another trend. Wikipedia says that “ The science concerning intermittent fasting is contested. The American Heart Association states that intermittent fasting may produce weight loss, reduce insulin resistance, and lower the risk of cardiometabolic diseases, although its long term sustainability is unknown. The US National Instittute on Aging (NIA) recommends against intermittent fasting because of uncertainties about its effectiveness and safety…. As of 2019, intermittent fasting was a common fad diet, attracting celebrity endorsements and public interest.” The entry goes on to say that “there is some limited evidence that intermittent fasting produces weight loss comparable to a calorie restricted diet. Most studies on intermittent fasting in humans observed weight losses, ranging from 2.5% to 9.9%. Alternate day fasting does not affect lean body mass, although one review found a small decrease.” Some other benefits of intermittent fasting include improved cardiovascular and metabolic signs for people suffer from obesity or other medical challenges.