I cannot find the study at the moment (Google you used to be great at this!) but there was one seeing how diabetics blood sugar was impacted from just fruit consumption. Got to the point where even at 20 serves per day (4 times the recommended) in most people it didnt cause an issue. Bundling that sugar with fiber was a big part of regulating sugars.

Corn syrup might or not be different, Im no expert in that field, but simply having highly refined sugars without the filler is monocropping your diet in weird ways. In the same way soil is being killed by mono cropped agricuture, we are doing the same with our gut biome. The flow on impacts are still being discovered.