It's genetics, not only food. Of course it's not an excuse to be fat fuck, but not every girl can be "lean", just will remain somewhat chubby unless they go overboard. And there's nothing wrong with being a little bit fat, it looks sweet on most girls!
Best example of genetics is one woman i know. She always used to it same food as me just maybe 3/4 of my amounts. I used to be fat fuck and she has veins on her stomach and crazy low bodyfat and remains muscular (for woman) without any exercise. Nowadays she just can't afford (financially) to eat that much shit, but back in the days her diet used to be all fastfood and chocolate in insane amounts. If she starts doing something, like walking long distance every day she can't cant eat enough and gets in "precontest" shape in matter of weeks. You know, abs visible, veins everywhere. It sounds unbielevable but yes, I see this every day and it makes you question your own abilities. Oh and despite short stature she owns in every sport there is and is naturally strong. She doesn't like that look and thinks it's ridiculous so she eats tons of food to look normal.