How do you increase the length of your fasts without stressing the adrenals?

Ask Dr. Jason Fung

What is the best way to come off a water fast? How do you increase the length of your fasts without stressing the adrenals? And how do you go about starting a low-carb clinic as an MD?

It’s time for this week’s Q&A about intermittent fasting and low carb with Dr. Jason Fung:

Best way to come off a water fast?

I am currently doing a long-term water fast and am wondering what you consider the best way to come off/get back into normal eating is.


Just be sure to do it gently. One of the risks of longer fasts (>5 days) is refeeding syndrome, which is mostly seen in underweight or malnourished people. I recommend low-carb foods because eating high carbohydrate foods stimulates insulin and increases the risk. Otherwise, eating too much too soon often causes stomach-ache, which is uncomfortable, but not dangerous.

Dr. Jason Fung

Increasing fasting periods

How can one increase fasting periods (from 18:6, to 20:4 to eventually 24 hours) without stressing the adrenals?


You just increase fasting times gently. It generally takes 1-2 weeks to get used to the longer fasting periods. Fasting is a stress on the body, and may increase cortisol. This is a normal physiologic response, so there is no getting around it. If you are prone to difficulty with high cortisol, or you feel your adrenals are not responding appropriately, then fasting may not work for you.

Dr. Jason Fung

Do you assist in starting clinics like yours?

I am a physician in Charlottesville, VA (semiretired anesthesiologist) who tried your diet quite successfully. I think the people in my area would benefit from a clinic like yours. What do you suggest I do to start one?

Gregg Korbon,MD

We provide dietary counselling online, so some of your patients may access it anywhere in the world. Check That way, you can provide medical guidance and have patients get their dietary counselling online. We have several levels of our IDM program. We provide lots of free materials for everybody. The next step, a membership community offers greater guidance with emails reminders, video Q&As, science discussions, private forums, and group fasts. We also offer direct small group counselling, which is the most expensive option.

Dr. Jason Fung



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Dr. Fung’s books The Obesity Code, The Complete Guide to Fasting and The Diabetes Code are available on Amazon.

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