My gal and I are pretty lit for being 50.
We actually decided to add a little chub over the last 8-9 months or so. She says she feels better 8 pounds heavier (5'7 @ about 140 now).
I noticed it's different with age, I used to bulk and it spread out easier, now it seems like it goes to my stomach first then everything gets bigger.
So I'll be back at working on my core here pretty soon.
When I was young and skinny/light grades 2-12 and almost to 30 years of age I would always catch a bug at least twice a year and get pretty ill for days or so. After gaining about 30 lbs into my 40s I got sick much much less, really sort of weird. And being even heavier I hardly ever get sick now. I never tried to research it.