We had dinner with JENNIFER ANISTON in Miami’s South Beach on March 8. Well, sort of. We dined at an outside table next to her at the Blue Door restaurant at the Delano hotel. It’s no surprise to see Jen in Miami – she’s in town through May filming “Marley & Me” with OWEN WILSON – but what caught us off guard was seeing the rail-thin actress eat BREAD at dinner. How can she eat carbs and stay so skinny? Perhaps the secret is the rest of her meal: Jen smoked a Marlboro Light, drank a glass of red wine and picked at a salad.