A data point, though my situation is not even about weight: I used to be skinny fat in my mid-twenties until mid-thirties - so basically still kind of slim but some belly fat and not much muscles. Kind of average, unremarkable.

After a breakup I started being more active again, I went bouldering once a week and gradually got into shape and then really athletic after about 2 years when I started going twice a week. My total weight didn't change at all. I dress just as good as before and have the same overall style. Of course most clothes simply look better on me, now that I'm more in shape. Same good job that I still like. I do go out a bit more. But overall I would say I really didn't change anything except getting more attractive from putting on muscles and losing fat.

It made a hell of a difference for dating. Before I felt mostly invisible but since then got approached in bars all the time, which rarely happened before. After some time I got way more confident - but when this stated I sure wasn't yet. Some woman even told me into the face that I lacked confidence after they approached me and realized I don't have the personality and/or confidence matching my appearance. They certainly only approached me because of my appearance.

The people only loosing weight are probably held back by other things. If they changed everything but their weight they likely wouldn't have more success either. I would say I had most things figured out already before and It seems I was held back only by having an average build. Just getting fit absolutely made the difference for me.