You know her: She eats an ice cream cone like no big deal. And you know she doesn’t always order salad. But she doesn’t have superwoman genes. So how come she doesn’t have to go on a diet? “Diets don’t work. They fail all the time,” says Carla Heiser, a registered dietitian and board-certified specialist in nutritional and metabolic medicine in Chicago. Here are the 10 rules your diet-eschewing pals live by—without having to think about them.