I have an athletic body, and I'm 105-110 pounds and exactly 5 feet tall. I ordered the small, and it is a lot less form-fitting than in the product picture on Amazon. It's more like sweatpants than tight, form-fitting jogger pants. It's very comfortable, but it's very loose-fitting around the legs and waist, and I have to pull the waist string super tight to make it stay on my hips. I would say it's great pants to lounge around the house in, or something to pull over your legs while you're warming up for dance class, but I would not jog in this, because it will most definitely be too loose and slide down my waist and legs if I started running in it. If you want comfy warm sweatpants that you can use to warm up your legs or be comfy in, these pants are great- but for running, I would recommend getting something more tight-fitting.