When I opened the app for my continuous glucose monitor (CGM) one morning, I got the following message “Don’t rely on the G6 app for monitoring.” WTF. It seems they are still working out the kinks with the current iOS system. Oh well. I would therefore put this in the category of ‘minimally useful.’
I wore the CGM for just over a week. Apart from the initial stab of pain on application and some soreness the first few hours, I really didn’t notice its presence. The readings did get more accurate (i.e. lower) as the days went on. Whether this is by chance, improved accuracy or me being more conscious of carbohydrates, I couldn’t say. I also did a 24 hour fast one of those days. But the monitor still consistently read over 100 mg/dL at night and rarely dipped below 100 mg/dL, even when fasting. I was reassured by the finger stick value but went to the lab for a blood draw to check insulin levels and get a gold standard value for fasting glucose. Both were reassuring. My fasting glucose was 87 mg/dL. This means my fasting glucose is not impaired. My fasting insulin was actually lower than the reference range. This implies that my pancreas is not pumping out tons of insulin in order to maintain normal glucose levels. Whew!
What lessons can I take from the CGM? Even without the benefit of the absolute values of blood glucose, I can see the trends. I didn't get the chance to have a beer to examine its effect on my blood sugar, but having an old fashioned did not seem to have much effect, despite the inclusion of a cube of sugar. The biggest spikes on average come after my breakfast. I typically have a bowl of overnight oats that includes half a banana, raisins, and sometimes some dried figs in addition to a mixture of nuts and seeds. This easily delivers over 100 grams of carbohydrate, comprising over 50% of its caloric content. I may consider dialing down the relative concentrations of dried fruit and increasing the nut concentration to make this meal tilt more towards fat and less toward carbohydrate.
I recently saw a meta-analysis that concluded that “light-intensity walking” was enough to reduce blood sugar after a meal. I can confirm that this works, having tried a 15-minute walk after downing a heaping plate of quinoa followed by a full plate of semolina pasta. I noticed a slight rise but no sharp peak in the glucose curve. This may be another reason for the post-oats rise in blood sugar, as I’m usually working shortly afterwards rather than walking. The researchers found that even simply standing provided advantages in glucose levels compared to sitting, though it was not as effective as walking. Although a 60 to 90 minute walk is the most effective, even just 2 minutes of walking is enough to modulate blood sugar. With many jobs, it can be hard to incorporate a walk, but a loop around the office or a trip to the bathroom or coffee machine can be just enough to get you moving.
Walking has many other benefits as well. It builds your cardiovascular base, the foundation for more intense exercise. It provides opportunity for social interaction. It facilitates thinking. It even promotes neuroplasticity, especially if moving through a new or unfamiliar environment.
What about the proverbial LBS, the ‘low blood sugar’ often blamed for a state of irritation or mental fog? During my week of CGM, I didn’t notice many troughs in blood sugar. It was mostly a flat line with peaks after meals. The notion of ‘low blood sugar’ making you hungry (or hangry) is not really based on science. One trough I did notice correlated with symptoms. The CGM was reading in the 60s, so perhaps my actual blood glucose level was even lower. Just before lunch, I had gone swimming in a not-so-warm pool, then finished it off with a cold shower, then a walk outside to my car with hair still wet. By the time I sat down to eat lunch, I was shivering and felt I could not get warm despite being indoors. Cold exposure with shivering thermogenesis (heat production) can increase carbohydrate metabolism. However, blood glucose only contributes to 10% of the heat generated, with most carbohydrate metabolized coming from muscle glycogen (glucose storage in muscle). After a pasta lunch and some tea I stopped shivering and was right as rain. Fun fact: Alaskan wood frogs that can survive freezing do so in part by stockpiling glycogen as part of a cryoprotectant system that protects their tissues from freezing.
For now, I will not be saying goodbye to carbohydrates. I will still carb load before and during endurance races. On the other hand, for anyone dealing with diabetes, metabolic syndrome, cancer or desiring weight loss, I think a low carb diet should be strongly considered. I will try to avoid using carbs as calorie filler, trying not to get more than 50% of my calories from carbohydrate. (I used to think nothing of crushing multiple slices of bread after dinner if I needed to top up.) Now, I will try to turn to a more fat-rich source of calories if I need satiety. Trying to get enough protein throughout the day helps modulate the carb overload as well. Lastly, I will also definitely try to spend at least a few minutes on my feet after a meal, especially if the meal is rich in carbohydrates.
Having satisfied myself that my high carb diet is not currently making me insulin resistant, the next question is whether I am unnecessarily triggering my immune system. For this, we will have to turn to that omnipresent component of the Western diet: gluten. Those suffering celiac disease have an extreme reaction to these proteins, but are those with milder symptoms or even no symptoms being adversely affected by gluten? Back to the lab we go…