Should I Diet First Before Starting An Exercise Program?

I'm just starting a cardiovascular exercise program and am about 140 pounds overweight. Should I start this exercise program now, or should I try dieting and wait to lose some of the weight first, and then start the program? I'm having difficulty keeping up in the classes and the movements seem really difficult.

You'll lose weight more rapidly if you combine calorie restriction with exercise rather than just restricting calories alone. If you're having trouble with the classes, you should try non-weight bearing activities, such as bicycling on a stationary bike, or swimming, or working on an elliptical machine which will protect your joints, ankles and wrists while you begin to lose the weight.