I am doing IF not just for losing some pounds but to also work at reducing or even reversing my type 2 diabetes. I have had some success over this last month, as I have done away with my use of Humalog at mealtime and have reduced my dosage of Lantus (looking to reduce it again next week)
My Blood sugars are typically in the 110 to 16 range during the day or even lower. However, I have noticed that when I go for a walk and check my blood sugar it can be in the 140-150 range. I presume this is just my body dumping the liver and burning fat but wanted to make sure I am not missing something.
this poster/info graphic might be interesting to review:https://brightspotsandlandmines.org/wp-content/uploads/2019/09/42FactorsExplainedOctober2019.pdf
came across it in this article:https://maori.geek.nz/the-unreasonable-math-of-type-1-diabetes-8c96bdf5b7fb
the poster says light exercise usually lowers blood sugar, but with higher intensity the adrenaline released can lead to a rise. so maybe something like that could be going on if the activity is new or strenuous, would be interesting to see if your response changes over time. Good Luck :)