Correct. You'll put on a small a mount of muscle in a calorie deficent diet and look more defined, fitter and athletic, youll do this simply by exercising muscles. You can tell the difference between someone who is fit and someone who has just lost weight, obviosuly. but to build muscle you need to train and then eat a high protein diet and because you need more calories it doesn't mean you can eat chips and burgers, it's lots of meats, veg. I know a bloke who got MASSIVE in two years by doing a weights workout then eating two tins of tuna straight after his session and two chicken breast a day in addition to a normal diet. they recommend 1g of protein for every pound of body weight as a minimum to bulk up so that's a fair bit if you're a 15 stone bodybuilder.