People that have used to be fat, and then lost a lot of weight, will know how brutally different people will treat you. Whereas you'd practically be a ghost before weight loss, random people will suddenly look you in your eyes, smile, even start conversations with you.

Some will of course argue that you losing weight will also make you more confident, and thus you become more approachable. I think there's a lot of bias against fat people, against "unattractive" people, etc.

This also shows in the classroom, work, etc.

Of course, actually being conventionally attractive will come with its own perks. People will go out of their way to help you, and to support you. Over time this could very well boost your ego to also become more confident and decisive.

>Some will of course argue that you losing weight will also make you more confident

Having been one of the people who experienced this (well the inverse, scarily skinny to lean and muscular), the confidence comes entirely from people in your life congratulating you, followed by strangers and new people just having a baseline positive glow towards you.

I don't know who came up with that line, it's repeated a lot, but I am almost certain it came from someone who never experienced the transition and soothed their ego by telling themselves it's all just a state of mind.