There’s something I’ve been thinking about for some time now:
What would happen if I, being a skinny person, were to gain a lot of weight? Obviously my skin would have to grow larger i surface in order to cover my body, but would that mean I’d get hairier as far as number of follicles go? I’m thinking it would. But what then if I lost the weight again, assuming the skin would shrink to fit me. I’d turn into an ape or what?
No, you do not get extra hair follicles through packing on th’ pounds, lammfile.
From this page on hair follicles.
Actually, the skin stretches out more than anything else (women are aware of this feature, especially with stretch marks after pregnancy).
So, no, if you blow up like a balloon then deflate down to normal, you won’t have to go touting for a part in Planet of the Apes. Welcome to the SDMB, BTW. 
Wow. That’s what I thought from the beginning, but then I thought it seemed weird.
I just thought of something else:
This means that i a person who’s fat and seemingly just as hairy as I am loses weight, he or she will be totally hairy. Unless the follicle become inactive or something…
that’s follicles, of course.
Dunno, lammfile. Changes in body chemistry, hormonal fluctuations, all have a part to play in the growth cycle of body hair. If you didn’t keep up the same nutrient intake levels during weight loss, you’d lose hair, not keep it. Hopefully, the RL medical experts will come along and provide more info.
With aging, many follicles that once were content to hold short, nearly invisible hairs begin to crank out thicker, longer hairs. Many folks get fatter as they age, so it seems that fatter=hairier. However, skinny geezers get hairier, too.
Hmmm…all the smilies are bald, except the Jewish one.