A number of really well informed and well intended views here.

My experience isn't typical, and is in no way advice... just me

I was always skinny, but a bit athletic. As a teenager, I was a bike racer and cross country runner to national finalist standards. Also was a rowing (crew) participant, and certainly used to pull my weight,

Which was 125 pounds to 6 ft 1 inch. I thought I was just great for my sports just then.

I was skinny because I was proto-diabetic. Wasn't diagnosed till I was about 20. By then, I'd stopped being athletic, maybe because I weighed 84 pounds by then

Now, 40 years on, I'm still a bit on the skinny side. Was about 140 lbs, through about 20 marathons and a lot of cycling. Currently 150, as I had a lay off of exercise following an accident, but now I'm back on the bike a bit more I'm progressing towards a happy zone of 145 or so