Well its nothing just body sturcture, any doc can explain it very well, and not all women have bigg ass..

Well I think it's lifestyle that affects how big a woman's ass gets. I've been married for 3 years and my wife is extremely lazy and hates any kind of sport related activity. My wife is 23 and she's gained 40 more pounds to her already chubby figure. Basically all of the weight went to her ass and thighs bringing her to 230 pounds at 5'6". Her ass is so big that she won't fit in our bathtub anymore and has to squeeze in, one time she got stuck. She loves her new weight and thinks it's sexier than ever and so do I! She usually wares really tight and revealing clothing which accentuate her curvy body and the rolls of fat on her chubby little belly. He ass is now 58" wide and it jiggles with every move. She also loves cook exellent food (being part French-Canadian). She wants her ass to get to 60" so we've hired a housecleaner so she has to do as little work as possible. She doesn't work so she basically lounges around on her ass all day stuffing her face with high calorie foods like cake, eclairs, doughnuts, ice cream etc... When I come home we'll cuddle up together she'll make her hair as sexy as possible, put on nice smelling perfume and plop her big soft butt right on my lap and I'll feed her chocolates while rubbing her belly. She's actually starting to get a permanent double chin! So I think for women, the secret to a big butt is just being lazy and eating alot. It's worked for my wife!