It can be difficult because of food addiction.

It should be noted that fructose is worse than other sugars because the metabolic pathway to break it down makes the liver work hard, similar to alcohol.

This longer metabolic path also makes it take longer to metabolize than sucrose or glucose, and so raises blood sugar more gradually. Its for this reason that pure fructose is actually a low glycemic index food (GI 20 vs 22 for cashews and 35 for sunflower seeds). For this reason I actually think fructose could be a very healthy sweetener in low quantities, but the problem, at least in the US, is that its added to almost every food.

I should also say that I don't think that glycemic index is a very good measure for various reasons that would make this comment really long if I went into them. Insulin index is much better but still not perfect IMO. Satiety value also seems really useful, since its basically a measure of how long a food makes you feel full per calorie. That doesn't replace the insulin index, since a food can make you feel really full and still be relatively insulin provoking (potatoes for example), but its something to look at in concert.

This is why I only eat fried cheese when dtunk