Here’s one for you. I was doing a long-distance cycle ride and wearing both a continuous glucose meter and a continuous ketone meter and this is what happened. But first some background.
All of the complicated algorithms for exercise in T1, assume a sugar fuelled metabolism ( so are of no use to me), and work on the assumption that in the pre-exercise period there is too much ‘insulin on board’.
Now, if we encourage ‘healthy’ carbs, in the high percentage that is the current practice in diabetes clinics, the body will be red hot on insulin dialled up to max. Ketones are impossible because insulin suppresses fat burning. Ketones are the energy molecules that result from fat burning. So, insulin promotes fat storage and suppresses fat burning.
Dialled-up insulin means insulin overload and because the insulin that is injected lasts hours to days rather than 15 minutes in someone without T1, that means a lot! So, the advice to T1 who want to exercise (and 60% don’t because it’s too scary with hypo fear), is to reduce insulin in anticipation of exercise and to eat glucose throughout exercise. It is the logical conclusion in a sugar burning metabolism. But anyone who does this knows how awful it is to have sugar in the stomach, indigestion, nausea, and stomach cramps.
I don’t do this. I keep insulin optimal and as a result I find that I rarely need glucose supplements during exercise but do carry them of course. Burning ketones and fat for energy reduces insulin requirements. I do all my exercise fasting and don’t need to adjust my insulin in anticipation of exercise so can be spontaneous about when I do it. Nor do I have to monitor for hours after exercise as all T1 exercise algorithms suggest. The reason? I don’t have too much ‘insulin on board.’
One of the effects of optimised insulin is that sometimes you don’t have enough insulin, a novelty to most.
So there I was on a fasted long-distance ride and I saw my glucose was rising. My ketones were also nudging up. Ketones will only go up if there is not enough insulin. Glucose likewise. So this was a case of too little insulin for my needs at the time. When I exercise I get insulin-sensitive. But I needed to replace that insulin. I added just one unit of insulin. A tiny amount, but I was going to be riding for a few more hours and didn’t want to overdo it.
And look what happened. Glucose reduced as predicted. But the reason for this blog is to highlight the ketones. We know that ketones stimulate insulin secretion which blocks fat burning and hence ketosis, there is another detailed blog about this here. With just a tiny amount of insulin, ketosis was suppressed.
So, if anyone tells you that a keto diet is a risk factor for diabetic ketoacidosis, they are wrong. Insulin is a potent inhibitor of ketosis, and that is why 75% of people with T1 have ketones in the low range of 0.5-1.5 mmol/l. Nutritional ketosis and diabetic ketoacidosis are different things.