The glycemic and insulinemic response to carbohydrates varies significantly based on food processing and structure, with refined sugars eliciting 2–2.5 times greater insulin response than minimally processed carbohydrates.

Study: The combined effect of gluten addition and semolina cell wall integrity reduces the oral sugar release and the insulinemic response to bread in healthy volunteers

This study found that bread made with coarser, less processed flour causes a smaller spike in insulin than bread made with finely ground flour, which supports the idea that how processed a carb is affects how much insulin your body releases.

Study: Effect of Processing on Postprandial Glycemic Response and Consumer Acceptability of Lentil-Containing Food Items

This study found that lentils that are boiled or mashed cause a much smaller spike in blood sugar than lentils that are turned into fine powder and dried — and since blood sugar spikes usually mean insulin spikes too, this supports the idea that refined sugars cause bigger insulin spikes than whole foods.

Study: Whole-grain cereal products based on a high-fibre barley or oat genotype lower post-prandial glucose and insulin responses in healthy humans

The study found that whole grains like barley and oats cause much less insulin to be released after eating than pure sugar — in fact, oats caused less than half the insulin spike of sugar, which supports the idea that refined sugars make your body release way more insulin than whole foods.