Ask our expert about diabetes and intermittent fasting

Ask Dr. Jason Fung

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

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

Here are a number of questions answered by Jason:

Dear Dr Fung

I fasted for 5 days straight, I only had water in this time as well as a cup of broth from bones on 2 occasions. I had no problems at all I had lots of energy and I slept well, and I wanted to keep going up to 7 days but stopped on day 6 because I developed horrible muscle pains in my upper back (as if my muscles were being stretched) I took electrolytes when the pain started and waited a 5 hours but the pain continued.

Would you know what would have been the cause of this?

(Over the years I have “fasted” over 8 – 12 hours often with no problems as I’m one of these people who forget to eat when busy, I am also currently 3 – 4 kilos over weight due to deviating from my low carb diet here and there over the last 12 months – I did my 5 day fast in this period… And I also hardly lost 1 kilo). I’m a 44yo lady.

Kind regards

Dr. Jason Fung: Muscle cramps are quite common and you may need to make sure you take sufficient magnesium, although not necessarily during fasting as it may cause diarrhea. Try Epsom salt baths and magnesium oil (on the skin).

Read more in the Diet Doctor guide on muscle cramps.


Hi Dr. Fung,
Considering a diagnosis of high cholesterol, Type 2 Diabetes and a fatty liver, should I not be worried about the high fat component in the lchf lifestyle affecting my cholesterol? Or would I have to go easy on the fat consumption and wait until my body enters effective ketosis for a considerable period of time before I can consume high amounts of fat.


Dr. Jason Fung: There is no correlation between diets high in natural fats and heart disease. I don’t believe that high fat diets are dangerous.

Read more in Diet Doctor’s guide on saturated fats.

Good morning Dr. Fung,
I have been following the LCHF way of eating for over a year. I test my fasting blood sugar every morning and I am now pretty much every day under 90 mg/dl sometimes as low as 70 mg/dl with fasting blood ketone levels above 1.0 mmol/L. My question is: how do I test whether I am insulin resistant? Is there a special test for it?
Thank you

Dr. Jason Fung: If you are not taking any medications, then either of fasting blood glucose or Hemoglobin A1C will be an accurate reflection of your insulin resistance. For more accurate testing, check your fasting glucose and fasting insulin levels and plug the numbers into an online HOMA calculator.

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


Intermittent Fasting for Beginners

More questions and answers

Many more questions and answers:

Intermittent Fasting Q&A

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. 1 comment removed
  2. satish
    Hi DR Fung,

    Thank you for your Video, which has changed my life. I been diabetes for more than 20 years with an average Hba1c ranging from 9 to 11. No matter how hard i tried it never work. I had a heart attack last year and was put on insulin. On insulin my diabetes started to get in control but i did not like as the doctor kept increasing the dose. The hba1c after i started insulin was 6.8 I woke 1 day and saw you video and decided to try it out. Walla, it work. I stopped insulin completely and my last hba1c was 7.5. i now have lost weight from 68 kg to 62 kg. the weight fluctuates like a yoyo 1 kg +/- daily, but now i can seem to go any lower although i am noticing lots of side sagging flab.

    My lowest fasting blood test in the morning is 5 to 7 in the morning now. Can you advise how can i lower the hba1c ? i asked my doctor he says once a diabetic, always a diabetic. Is that true?

    Once again, thank you for giving me a new lease of life. God Bless.

  3. Colleen
    Is there a video that provides information on leptin resistance. What I"m reading, I should have protein in the morning, I should only complete short-term fasting, and other conflicting information.

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