Do you have a citation for 15-30 minutes being a reasonable time for blood glucose levels changing in response to consuming a banana? I remember reading that it takes significantly longer than that, up to 150 minutes, but I can't find a proper source at the moment. The closest I can find is the 4-hour body, and I don't know how trustworthy it is. It also says that fructose may lower blood glucose levels.
I don't, actually. I ran a year long informal experiment on myself, trying to measure my metabolic rate / caloric need per hour, and have a recollection of reading that ingesting a banana before a workout should provide enough glucose for an hour (I don't think it specified for what activity; I found that the banana lasted for the first forty-five minutes of a treadmill 10k run at a pace fluctuating between ~4:30 and ~6:00 minutes per kilometre*) - both probably inform that 15-30 minute figure. Your metabolic speed will vary, and not necessarily within that range.
*By "last", I mean a subjective sense of being energized and having enough fuel. I realise now that may not be a reliable indicator.
This is the public group instrumental rationality diary for June 1-30; it's going up pretty late (sorry!) but entries for earlier in June are welcome.
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