T1 runner following Dr Bernstein regime

I am a 56 year old T1 and started following Dr Bernstein’s regime 10 weeks ago. I’m following it strictly and eat less than 30 g of carbohydrate per day. It has been transformational in terms of blood sugar control. I am incredibly grateful to him.

I’m wondering whether anyone has experience of following Dr Bernstein’s regime as a runner. My local diabetes specialist had previously advised that I should not even think about running if my blood sugars are below 130 mg. However, my blood sugars are frequently 90 mg or less these days. I tend not to run for more than 30 minutes at the moment but have had no problems at all. I run nearly every day.

Of course, I am now running primarily on ketones rather than glucose.

Does anyone have experience of running much further on the Dr Bernstein regime, say one hour or longer? Has it been necessary to supplement with glucose? I would be most grateful to hear of any experiences. Thank you very much.

This specialist is not taking into account the much lower insulin total daily dose you now take and how that dramatically brings down insulin on board. A low IOB combined with greatly reduced glucose variability eliminate the need for buffering your exercise with a starting BG of 130 mg/dL.

That doctor was advising the typical diabetic, not you, and was overly concerned with liability at the expense of your quality of life. I understand why that happens but it’s as if he was not listening to you or did not understand the consequence of a low carb lifestyle on a T1D athlete.

I am not a runner but I have spent a fair amount of time bicycling in my past and I think the doctor’s advice is not relevant to you. What I would recommend is for you to wear a continuous glucose monitor so that you can learn how your body works when exercising. You will then be able to strategically deliver small amounts of food and insulin at just the right moments to enable robust and successful running.

Exercise is the magic catalyst that propels all good glucose management. Keep up the good work!

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I used to run for about 80 to 100 minutes. I always had to supplement after 30 min and 1 hour and about every 30 min depending on activities. I supplement any where from 15 to 25 carbs and I turn off basal about 2 hrs before I start most times. I am not on Berstein’s program. Also if you are doing the same amount of exertion daily the additional amount of extra glucose drops off.
" What I would recommend is for you to wear a continuous glucose monitor so that you can learn how your body works when exercising. You will then be able to strategically deliver small amounts of food and insulin at just the right moments to enable robust and successful running."
this is good advice because everyone is different

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Thanks so much for the advice! Much appreciated.

Many thanks for sharing your experiences and thoughts!

I have the same experience as @typ1 and I concur with the above comment! I’m also NOT on the Bernstein diet. I frequently run 2+ hours and always supplement with carbs during the run as needed per BG. I usually start the run (or within 2 miles of start) with 21g carb gel and take addl small amount of carbs as needed during the run. I may bolus a small amount (eg., 0.15U for 21g) for the carbs if it looks like I need it. I aim to stay in BG range of 60-120, and I monitor my BGs w/ my CGM on my Apple Watch.

Good luck with your running and control!

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Many thanks for your thoughts and encouragement!

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Hi @Hugh_Shields
It really depends on your goals and the intensity level of the exercise. You can certainly do long distances on a low-carb regimen. But you cannot do them as fast as you can on a higher-carb regimen.

With a slower pace, your body is able to use fat as its primary fuel source.

The respiratory exchange ratio (RER) is the amount of carbon dioxide (CO2) produced by the body divided by the amount of oxygen (O2) consumed by the body.

When using fat as a fuel, we create less carbon dioxide for a given amount of oxygen used than when we use carbohydrate as a fuel.

For 1 molecule of fat to be used for energy, 16 carbon dioxide (CO2) molecules are produced, and 23 oxygen molecules (O2) are used.

In comparison, to oxidize 1 molecule of glucose, 6 CO2 molecules are produced, and 6 O2 molecules are used.

An easy analogy to think about is that when you are walking, it is easy to talk. Then you start jogging slowly, you can still talk. Eventually the faster you go, talking full sentences becomes hard and you can only say words with gaps between. And if you are running hard enough, you really can’t talk at all.

It can be managed on low carb if you cut your basal correctly before the exercise and your pace allows your body to primarily still use lipids for fuel. You can also use your heart-rate to get a rough estimate for what pace will allow you to primarily use fat.

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Many thanks for your advice!

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Dr. Bernstein uses liquid glucose to maintain his BG during exercise. 1 gram of glucose at a time. I know he talked about this on his Youtube channel once so you may be able to find the video where he explains his process.

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Thanks so much for highlighting this.