The entire yoke of my mother's side of the family is overweight or obese, my sister was obese as a child at one point, and I was overweight at one point as well – so I've dealt with this kind of stuff.
Being overweight or obese causes a lot of psychological harm to the person that's overweight, simply because of lethargia and other self-esteem factors that come with it. In a sense, you tend to feel worse more often if you're overweight than if you're not.
So, this study is correct, but what's its point? Don't shame fat people? Maybe. I feel a lot better about myself and others when I lost my excess 40 pounds I was carrying in my gut, and I'd like to stay that way.