Alternate-day fasting, as the name suggests, involves fasting every other day. So, if you were to follow this fasting schedule, you would eat normally one day and fast the next day.
The alternate-day fasting protocol has gained popularity largely due to the research of Krista Varady, Ph.D., a professor of nutrition at the University of Illinois, Chicago. In her book The Every Other Day Diet, Varady describes how you can lose weight by eating what you want—half of the time.
The idea behind alternate-day fasting is that instead of having to limit your calories every day, as many diet regimens require, you only have to restrict your calorie intake on alternate days.
When you fast, your body starts to burn stored fat for energy, a process known as lipolysis1. Over time, it goes into a metabolic state known as ketosis2, where it uses fat as its main source of energy, instead of sugar.
When done correctly, ADF can also give you the benefits of fasting beyond weight loss. Emerging research shows that alternate-day fasting can be a useful tool for improving metabolic markers, boosting heart health, lowering chronic inflammation, and promoting cell repair, says Madiha Saeed, M.D., an integrative family physician and author of The Holistic Rx.
However, most people will find fasting every alternate day challenging. Furthermore, this diet may not be safe for everyone and should only be undertaken under medical supervision, says Bindiya Gandhi, M.D., an American Board-certified physician who practices family medicine and integrative medicine.