Fructose and fats are both handled by the liver. I'm going to include saturated and monounsaturated fats along with PUFAs when I talk about this theory. When you eat fructose and fats together you may create an excess load that the liver is not very effective at handling. The way to eat fructose and fat is by making sure they are not in the same meal.
There are a couple of good things about this theory. The good news is that dextrose does not have fructose in it but is still an effective sweetener and should not cause the reaction. If eating a meal with fat in it, consider using dextrose as a sweetener in place of sugar or HFCS. You also might consider drinking diet soda or using artificial sweeteners when eating meals with fat. But when not eating fat, fructose should not be a problem.
The question in my mind is "How long should a person wait after their last meal before consuming fructose or fats?" I would consider the diet of the Kitavans. They eat starch and fat for breakfast, fruit for lunch, and starch, fat, and protein for dinner. This effectively keeps fructose and fats separate. One could estimate a separation of about 4 hours between meals.
What gave me a clue to this theory was the diet of Jeanne Calment. She lived to be 122 years old. She ate about a kilo of chocolate per week. That is about 2.2 lbs. of chocolate which has BOTH fructose and fats. So why did she not become obese? I think the secret was that she had an incredible liver. Keep in mind that her husband died from eating a dessert with tainted cherries, but she did not die from it. My guess is that her liver was much more capable of detoxifying the dessert than her husband's liver.
Chocolate may not be a superfood, unfortunately. It may have just been a passionate pleasure that helped to reveal the remarkable liver of Jeanne Louise Calment.
What about milk? It seems milk may pose a problem. The lactose in milk breaks down into glucose and galactose. Galactose is then changed into glucose by...the liver. If I were trying to avoid the reaction, I could drink cream. Butter also does not have lactose in it and shouldn't be a problem. But I would avoid milk and cheese if trying to reverse obesity. Goat's milk also has lactose.
I would not expect a quick recovery from obesity following this theory even if it is true. But the rules are simple enough and easy to follow...avoid eating fructose and fats at the same time.