Treadmill making legs bigger?

CSIMelissa

I am thin and a very healthy eater but want to tone up and am also wanting to reap the health benefits of more exercise. I have been walking on my treadmill for about 2 weeks and I'm noticing that my pants are fitting tighter in my calves and thighs. Is it typical to get bigger as you are starting to tone? Will it ever stop? Should I scale back my exercise or intensity? I walk for 20 minutes ranging from 2-3mph, 5-7 days a week. (I've noticed in the past when I do weight bearing exercises too that I tend to firm/bulk up quickly so it may just be in my genes.)

Maybe I'm just paranoid, but a few years ago I lost 65 lbs and I'm very happy with my size now, but a little toning wouldn't hurt.

RGv2

Glycogen stores and water retention...most likely.