I just watched a fascinating presentation by Dr. Chris Knobbe, whose thesis is that diabetes and obesity may be more the result of too much polyunsaturated fat in our diet, quite apart from the effects of glucose and fructose. He makes a persuasive case, and if he’s right, you might try using a small quantity of seed oil (cottonseed, sunflower, safflower, rapeseed/canola, peanut, etc.) in your food to see if it contributes to weight gain.
Here’s Dr. Knobbe’s presentation. See what you think: