"For better health and a longer life span, exercise is more important than weight loss, especially if you are overweight or obese, according to an interesting new review of the relationships between fitness, weight, heart health and longevity. The study, which analyzed the results of hundreds of previous studies of weight loss and workouts in men and women, found that obese people typically lower their risks of heart disease and premature death far more by gaining fitness than by dropping weight or dieting."
Both are, of course, very important.