Dr. Jason Fung answers questions about intermittent fasting

Ask Dr. Jason Fung

Do you want to know more about intermittent fasting for weight loss or diabetes reversal? Learn from Dr. Fung’s answers to common questions. He’s a Canadian nephrologist and a world-leading expert on intermittent fasting and LCHF, especially for treating people with type 2 diabetes.

Here are a number of questions answered by Jason:

High morning blood sugar

Dr. Fung,
I have read and re-read everything on your blog and this site for nearly a year. I have T2D and have been following LCHF, and doing some IF. I currently take 1000 mg of metformin. This was recently reduced because my A1C came down to 5.2! I feel great about the progress I have made but the dawn phenomenon still has me puzzles. My numbers in the morning are always in the 130’s. I want them lower!

Should I not be concerned about this? I have read your blog about DP, but I’m not quite sure if you are saying that high numbers in the morning don’t matter or if I should expect to see them come down in time. It seems to me that recently my morning numbers have gone up- Can you clear this up for me?

Dr. Jason Fung: Your DP indicates that you have not entirely gotten rid of insulin resistance. Sometimes it just takes more time. Insulin resistance is a time dependent phenomenon. It can take years to develop and can take months-years to go away.

I wouldn’t worry particularly about it. But it does mean you have more work to do.

Read more in Diet Doctor’s guide to insulin resistance.


Is drinking broth really fasting?

Dear Dr.Fung,
Thank you very much for all your help and for the lovely website,
I was just wondering regarding the broth, how come we can have it during the fasting since I believe it contains some fat/ some proteins/ and some calories from the bone and meats which are boiled… I’m just thinking aren’t we are better off without it and stick to water tea, for a proper fast?
Thank you

Dr. Jason Fung: Yes, the broth technically breaks the fast. We use it more in extended fasts for 2 reasons. First, the small amount of protein makes very little difference to most people. Second, it reduces the risk of re-feeding syndrome. If you would like to stick to water fasting, that is fine, too.


Should I eat more often?

Dear Dr. Fung,
This is one of the best life changing regimen I have ever done and it is showing great results in my blood work as well, recently I’ve been going through a body fast were I wake up not hungry and eat only when I feel the need to (still trying to control that, wait too long I guess before eating) as well I workout twice a day.

Do I continue with this concept where I eat when I need to or time it in a way to eat every 8 hrs, it’s very confusing since I am still considered a Diabetic (hopefully not for too long).

Just to add, I was diagnosed as a diabetic in Jan 2015 with A1c of 6.5; Lantus 8 units; 1000mg Metformin and before the diet the A1c was 5.5 on Oct 2015, now after 3 months my A1c is 4 and recently taking 500 mg Metformin and no Lantus (had to reduce/remove since I went into hypo a few times). Sadly I live in Bahrain and there are no Doctors that agree to this diet and no one to support, so doing this on my own with experimentation and checking my results on a monthly basis (family has a history of BP and Diabetes with other health issues like GERD and hypertriglyceridemia which I think this is norm with T2D).

I’m guessing I am doing it right since I have done the research and saw almost all your content on the site with monthly blood works.

Dr. Jason Fung: If you are not hungry, you should not eat. That is your body telling you that it has enough energy. Where is it coming from? Your own fat stores! That’s excellent. So, continue to let your body burn the fat and don’t eat.


Intermittent Fasting for Beginners

More Questions and Answers

Many more questions and answers:

Intermittent Fasting Q&A

Read all earlier questions and answers – and ask your own! – here if you are a member:

Ask Jason Fung about intermittent fasting and type 2 diabetes – for members (free trial available)

Read Dr. Jason Fung’s new great book The Obesity Code for many more insights:

The Obesity Code

More About Intermittent Fasting and Diabetes

What is Fasting? – Dr. Jason Fung
How to Maximize Fat Burning – Dr. Jason Fung
How to Fast – The Different Options – Dr. Jason Fung
The 7 Benefits of Fasting – Dr. Jason Fung
The Top 5 Myths of Fasting – Dr. Jason Fung
Breakfast! Is It Really That Important? – Dr. Jason Fung
The Most Common Questions – Dr. Jason Fung
How to Get Started with Fasting – Dr. Jason Fung
Who Is Dr. Jason Fung?
The Perfect Treatment for Weight Loss and Diabetes – Dr. Jason Fung
The 2 big lies of type 2 diabetes – Dr. Jason Fung
The Key to Obesity – Dr. Jason Fung


  1. Chris Roberts
    Do you have any suggestions for someone who wants to fast but has acid reflux? Can I take apple cider vinegar, baking soda and lemon water to help with it? I do take prevacid, but sometimes it still pops up during the day and finding on this fast day I am feeling the reflux. Thanks
  2. Dorothy Krause
    I told my 40yr old daughter, who is obese, that I was on a 3 day fast (I'm at goal 57 kg). I was hoping this would be a gentle way to tell her about fasting. Well she told her Exercise Physiologist who told her " get in touch with your mother tell her, her muscles are being destroyed and particularly her heart muscle". Well it sure did rattle me. I've read the OC and TCGTF as well as many other books, listened to the podcasts, the webinars and have been an active participant on the Support FB page. I have lost a lot of confidence. Am seeing my dr and having bloods done this week. (I do this 6 monthly.) Apart from some palpitations which a dose of salt has fixed I'm 68 and in pretty good shape. Walking regularly for an hour.

    I need your reassurance.

  3. Gina
    I am currentlyon dialysis I am also a diabetic has kidney failure and have hypothyroidism I would like to know if fasting is safe for me.
  4. Helen
    Is it okay to fast when you have benign pvcs? I get alot of them when I don’t eat enough. So scary! But, I really want to fast longer than 16hrs.

    Thank you!

  5. Paula
    I am T2D. I am in the middle of my first 36 hour fast. I always have higher BG in the morning. I thought the fast would help with that but my BG reading was still up higher than before bed. I have read about the DP. I am just not sure what to do?
  6. Shay
    I work 11 hr shifts . I sit most of the whole day. I bring a lunch which I pick at all day . It's a small lunch . I stretch through the day . I have a right side near shoulder blade pain which is caused by muscle flare . I can touch my toes . Im 54 and now im gaining weight it my mid section . I really don't know what to do to loose the weight .
    Reply: #7
  7. Kristin Parker Team Diet Doctor

    I work 11 hr shifts . I sit most of the whole day. I bring a lunch which I pick at all day . It's a small lunch . I stretch through the day . I have a right side near shoulder blade pain which is caused by muscle flare . I can touch my toes . Im 54 and now im gaining weight it my mid section . I really don't know what to do to loose the weight .

    You may want to try our free two week challenge!

  8. Denise
    I have heard somewhere that Intermittent Fasting can cause an increase in Cholesterol? I have been watching what I eat (loosely follow fast800), increased good fats, exercise daily (walking 50 mins at decent pace - osteoarthritis in hands and feet), fast between 14 - 20 hours regularly,.. but my recent Cholesterol blood test showed high chol - so much that my doctor has put me on medications.. I am trying to avoid medications.. but I also know the risk of CKD due to both hypertension and high cholesterol.. can you point me in the right direction so I can have another 'robust discussion' with my GP.. (evidence based preferred) Thank you in advance.
  9. Bob
    Dr Fung, what do make make of this Yale study that links intermittent fasting with Type II diabetes ? https://news.yale.edu/2020/02/04/studies-suggest-new-path-reversing-t...
    Reply: #10
  10. Gentiann
    I just read this report and did not see a reference to intermittent fasting.
    I understood that the fast refered to was the overnight fast when the liver produces glucose to keep blood sugar from falling too low. They found that normally the liver can switch off the production of glucose when not needed but that this switch is not working in diabetic mouses. The team from Yale is trying to come up with a drug to fix this problem.
    I have a better idea:
    not overloading the liver with sugar by eating a very low carb diet.....!

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