WHAT
Fasting is the willful refrainment from eating and sometimes drinking.

From a purely physiological context, "fasting" may refer to the metabolic status of a person who has not eaten overnight, or to the metabolic state achieved after complete digestion and absorption of a meal.

Several metabolic adjustments occur during fasting.

WHY
There are numerous benefits of fasting. Here are some:

• Promotes Blood Sugar Control by Reducing Insulin Resistance
• Promotes Better Health by Fighting Inflammation
• May Enhance Heart Health by Improving Blood Pressure, Triglycerides and Cholesterol Levels
• May Boost Brain Function and Prevent Neurodegenerative Disorders
• Aids Weight Loss by Limiting Calorie Intake and Boosting Metabolism
• Increases Growth Hormone Secretion, Which Is Vital for Growth, Metabolism, Weight Loss and Muscle Strength
• Could Delay Aging and Extend Longevity
• May Aid in Cancer Prevention and Increase the Effectiveness of Chemotherapy

HOW
Here are a few of the most common types of fasting:

• Water fasting: Involves drinking only water for a set amount of time.
• Juice fasting: Entails only drinking vegetable or fruit juice for a certain period.
• Intermittent fasting: Intake is partially or completely restricted for a few hours up to a few days at a time and a normal diet is resumed on other days. Typically windows are: 
  • Fast for 12 hours a day. 
  • Fasting for 16 hours (called the 16:8 method or the Leangains diet). 
  • Fasting for 2 days a week. People following the 5:2 diet eat standard amounts of healthful food for 5 days and reduce calorie intake on the other 2 days.
  • Alternate day fasting. There are several variations of the alternate day fasting plan, which involves fasting every other day.
  • A weekly 24-hour fast. Fasting completely for 1 or 2 days a week, known as the Eat-Stop-Eat diet, involves eating no food for 24 hours at a time. Many people fast from breakfast to breakfast or lunch to lunch.
• Partial fasting: Certain foods or drinks such as processed foods, animal products or caffeine are eliminated from the diet for a set period.
• Calorie restriction: Calories are restricted for a few days every week.

Check out the fasting category under Recipes for more details on each fasting