‘Can you have a normal blood sugar and still be insulin resistant?’

Ask Dr. Jason Fung

Why does my blood sugar rise when fasting? Can you have a normal blood sugar and still be insulin resistant? And can resistant starch be eaten on a keto or low-carb diet?

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

Why does my blood sugar rise when fasting?

When fasting, I notice my blood sugar rises instead of dropping. Why is this and how do I correct it?


It’s due to the counter-regulatory surge. Normally, as insulin falls, other hormones go up. As these run counter to insulin, they are called the ‘counter-regulatory’ hormones. These include activation of the sympathetic nervous system, noradrenalin and growth hormone. The normal purpose of these hormones is to increase blood glucose. During fasting, insulin drops and these hormones go up, so blood glucose may go up instead of down.

Is this a bad thing? No. Not at all. After all, if you are fasting, where did this glucose come from? It could only have come from one place – your own body stores. So your body is liberating this stored glucose for you to burn during fasting. A completely normal phenomenon.

See posts on the Dawn Phenomenon for explanation.

Dr. Jason Fung

Can you have normal blood sugar and still be insulin resistant?

Hello Dr. Fung,

Can one have normal HbA1c and be insulin resistant?

Thank you,

Yes. There are many different manifestations of insulin resistance, only one of which is elevated HbA1c. I prefer to call these manifestations of ‘hyperinsulinemia’ instead of insulin resistance. Hyperinsulinemia causes all of the facets of the metabolic syndrome including high blood pressure, high triglycerides and low HDL, increased abdominal obesity and high blood glucose (which can be measured by elevated A1C). Sometimes hyperinsulinemia is manifested by abdominal obesity and other time, elevated blood glucose (type 2 diabetes), but the overall problem is the same.

By calling it hyperinsulinemia rather than insulin resistance, the solution becomes obvious. If the problem is too much insulin, then lower it. How? LCHF diets and intermittent fasting.

Dr. Jason Fung

Resistant starch on keto or low carb?

Can resistant starch be eaten on a keto or low-carb diet?


The data on resistant starch is very preliminary but extremely interesting. Resistant starch are starches that are not absorbed by the body and therefore act more like fibre than starch. Potatos that are cooked and then cooled, for example, may develop resistant starch, which may then not be as bad as regular starch in terms of blood glucose. However, there are no firm answers yet.

Dr. Jason Fung



Intermittent Fasting for Beginners

Earlier Q&A

Intermittent Fasting Q&A

Q&A videos

Top Dr. Fung videos

More with Dr. Fung

Dr. Fung has his own blog at intensivedietarymanagement.com. He is also active on Twitter.

His book The Obesity Code is available on Amazon.

The Obesity Code

His new book, The Complete Guide to Fasting is also available on Amazon.


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