The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting

by Jason Fung

Fasting is simply the most efficient and effective way to lower insulin levels. Notice, however, I did not say it was the easiest. But do you want a method that is easy, or a method that works?

Head-to-head studies reveal that fasting is actually superior to bariatric surgery in both weight loss and reduction in blood sugars. Both methods are also effective for type 2 diabetes. So here’s the crucial question: If all the benefits of bariatric surgery come from the sudden and severe reduction in calories, why not just fast and skip the surgery entirely? In essence, fasting is bariatric surgery without the surgery.

There are many different fasting regimens, and there’s no “best” one. They all work to different degrees for different people. One regimen may work for one person but be utterly ineffective for the next. One person may prefer shorter fasts while another prefers longer ones. Neither is correct or incorrect. It is all personal preference. Fasts can range from twelve hours to three months or more. You can fast once a week or once a month or once a year.

the combination of whole foods, lower-carbohydrate diets, less added sugars, and a daily twelve-hour fast was enough to prevent most Americans in the 1950s and 1960s from developing obesity—even though they still ate plenty of white bread and jam, and whole-wheat bread was rare and whole-wheat pasta unheard-of.