I went from being a scrawny guy in my teens, to a chubby/fat gamer in my late teens/early 20s, and then a fit athlete in my mid 20s. While I had envisioned much more interest from the ladies, my biggest surprise was how much nicer, kinder, and helpful random people were. And in a professional setting, co-workers and leaders just treated you more seriously - especially when it came to handing out leadership roles on projects etc.

Also helps to not be a teenager.

I was in the best shape of my life after religiously going to the gym for ~3 years in my late twenties.

Outside of a couple of women asking me for help at the grocery store with some heavy produce, it barely made any difference to how people treated me.

Being fit is just 1 aspect. These days you also have to look like you're a top 20% in a bunch of other categories as well.