My wife did her first half marathon on Saturday at age 49. Knowing her the way I do, I do know that her weight has little to do with running nor does her running have much to do with her weight. She does have a very strong will and is very conscious of her health. I think her will preceded her weight and her running. She doesn't weigh less because of running nor does she run more because she's thin. She's thin and runs because her will is so strong.