Come on. Everything in the study belies these mealy-mouthed conclusions. To resist a fattening norm, you need willpower. To reverse it, you need to promote responsibility, which implies blame. You almost certainly need stigma. And realistically, to add normal or underweight friends to your circle, you have to relegate others who are overweight. That may be bad for your fat ex-friends, who will lose your friendship as well as your thinness. But it's fine for you, since you'll have just as many friends as before.
Maybe it's not nice to speak these truths. But maybe being nice, when you should be speaking the truth—especially to your friends—is the problem.