Exercise is always good for overall fitness and helps in losing weight, but your food intake with an eye on total calories is important in weight control.
What's your diet like? What's your body type like? Are you overweight? As for calories, they're not the most important tool for choosing a diet -- some high calorie foods are very good for losing weight, some low calorie foods are bad for losing weight. The real issue is how you metabolize and digest your food, and that will differ by the person.
Diet should go with exercise for the weightloss to be effective.