"Starch and glucose efficiently stimulate insulin secretion, and that accelerates the disposition of glucose, activating its conversion to glycogen and fat, as well as its oxidation. Fructose inhibits the stimulation of insulin by glucose, so this means that eating ordinary sugar, sucrose (a disaccharide, consisting of glucose and fructose), in place of starch, will reduce the tendency to store fat. Eating “complex carbohydrates,” rather than sugars, is a reasonable way to promote obesity. Eating starch, by increasing insulin and lowering the blood sugar, stimulates the appetite, causing a person to eat more, so the effect on fat production becomes much larger than when equal amounts of sugar and starch are eaten"
From https://raypeat.com/articles/articles/glycemia.shtml