Everything I've been reading about diabetes, blood glucose, insulin indicates caffeine in excess causes a rise in insulin. I know when I do my morning blood glucose testing, if I don't have coffee with caffeine it stays in the "usual" range, but if I do regular coffee I get about a 5 point spike. You could test your bg and see if you get a reaction--home test sytem is inexpensive.
I was a sugarbaby; meaning since I was born I was given lots of sugar, and ate lots of processed foods, especially sweets until I was into my thirties. Most people in the west were/are sugarbabies.
“How does today’s youngster educate his sense of taste? By submerging it in a sea of sugar from the time he gets up to the time he goes to bed.” W. Root and Richard DeRochemont, Eating in America (1976)