I discovered that you can buy a 2 week Continuous Glucose Monitor (CGM) for $65, more details here:
Here is an example of a typical day of my measurements:
I’ve been doing the ‘time restricted’ eating thing for about a year, with a eating window between 6pm -> 10pm. The rise between 9 -> 10 am is from a morning exercise routine.
Here is a summary for 2 weeks of a mostly consistent routine:
For another 2 weeks, during the post-exercise afternoon fasting window, I tested how my blood sugar reacted to 100 calories of 30 different foods.
These photos are sorted by weight, scale is in ounces:
Putting 100 calories of various foods on a scale really made an impression my naïve stomach. A full bowl (10 oz) of delicious strawberries has the same calories as a handful of peanuts, or 0.7 oz of peanut butter or chocolate!
I downloaded the data from libreview.com (button on upper right of glucose history page), then imported to this google sheet. I manually tweaked each test to make these charts, sorted with highest peak first:
As expected, the high sugar foods and fruits had the highest peaks. Raisins and grape juice had similar peaks to pure sugar! I used to love raisins 🙁
Also as expected, high protein or fat foods were pretty flat. An interesting note is that wine was also flat, even though it is basically fermented grape juice.
The amount of sugar is what determines the peak response. Here are 50, 100, and 200 calories of raisins, corresponding to 11, 22, and 44 grams of sugar:
Mixing in a high fat or protein food seems to help blunt the sugar response a little. Here is bananas & yogurt:
Here is raisins & peanuts:
So what is my take away? Blood sugar spikes trigger the release of insulin, and if this happens too often, you become numb to it. This is what leads to diabetes, so minimizing spikes seems like a good idea.
For my body, this means avoid eating foods with 15+ grams of sugar (e.g. a handful of raisins). Eating bulky high fiber fruits is good (fills me up) as long I limit it to one serving and/or mixing it in with other foods.
But every body is different (e.g. muscle mass, gut biome), so your mileage may vary. The only way to know for sure what can raise your blood sugar level significantly is to measure it. Don’t let the needle scare you 🙂