Big Tasty, Royal and six nuggets — followed by the gym

Forty grams of carbohydrates from a fast food restaurant, and the reading rose by six. That sounds like good news — but it is only half the story.

Fig.: The curve on 22 July. The dashed line marks the meal, the shaded area the training session. 72 individual sensor readings.

What the sensor recorded

140

mg/dl · before

Starting value at 2:33 pm

146

mg/dl · peak

Highest reading at 3:13 pm

mg/dl · rise

With 40 g of logged carbohydrates

100

mg/dl · after

Lowest reading after the session

Readings from my own sensor, 22 July 2026.

What was on the tray

Big Tasty Bacon, Hamburger Royal TS and six chicken nuggets. I logged forty grams of carbohydrates in the app — a rough estimate, I do not know the exact figure.

What came afterwards

About an hour after the meal I was at the gym: fourteen minutes on the stepper, then strength work, and another ten minutes on the stepper at the end. Around an hour in total.

The decline falls exactly into that window. The peak was 146; forty-five minutes later the reading stood at 100.

What this does not show

This article does not show that fast food barely moves blood sugar. It shows what happens when a large meal and an hour of exercise come together. What the curve would have looked like without the session, nobody knows — I did not test that on this day.

Why it is still interesting

Muscles take up glucose during and after exertion, largely without insulin. The effect is well described. What surprised me was the scale: a meal I would have written off as a slip stayed unremarkable in the record.

The reverse does not follow. It does not mean everything can be trained away. It means the timing of movement matters.

How reliable is this?

A single observation. Two factors acted at the same time — the meal and the training. They cannot be separated from this reading. For a clean answer I would have to eat the same meal without training, and I did not.

Key points

Forty grams of carbohydrates, a rise from 140 to 146 mg/dl.
About an hour later: stepper, strength work, stepper again.
During the session the reading fell to 100 mg/dl.
Meal and movement acted together — they cannot be separated here.
Without the training the curve would probably have looked different.

Single observation, not a study.

Sources

This entry is based on my own sensor readings. Where studies are mentioned, they are linked in the text. Continuous glucose monitoring: FreeStyle Libre 3.