I bought an old Woman's Day magazine (1980) in a thrift store (for a crochet pattern that was on the cover), and was reading the articles.
Inside was an article advocating high fructose syrups as sugar-replacements, because they were sweeter per calorie than other sugars, and therefore (the logical conclusion was that it would be) a weight loss aid.
One thing to remember though with the rat studies, is that rats can't go shopping for food, can't decide on and stick to a calorie budget, experiment with different food plans, or write in their little food journals to discover patterns they'd like to change, and then experiment and evaluate those changes.
It's far more likely that a human being could incorporate HFCS into a healthy diet, than a rat. How can it be done? How difficult is it? Is it worth the effort? All of those are part of the equation that can't be determined with rat studies.
For example, the study that showed that aspartame-sweetened water increased rat's appetite for sweet foods (compared to unsweetened water).
This study has been used to support arguments that weren't even addressed in the study. For example "eat real sugar, because aspartame makes you hungrier than "real sugar." That WAS NOT studied. Regular sugar may trigger the sweet tooth as much or more.
I do use artificial sweeteners, and I do recognize that they might intensify sweet cravings - but unlike a rat I can stick to my exchange plan/calorie limit. If I couldn't monitor my food intake, it would be a bigger issue, but since I can it's an entirely different issue.