The diet is going to be way more important. Cardio ain't all its cracked up to be.
Here is a little something for you:
Why exercise doesn't burn many calories
Go to the health club and climb on a stair stepper or treadmill. Program the machine by plugging in your weight, select your speed or program and begin your workout. As you plod along on the apparatus you are driven along by the ever-increasing number on the screen that indicates the number of calories that you have burned. Eventually you go long enough to burn 300 calories and you are left with a feeling of accomplishment. Now, as you wipe the sweat from your brow and catch your breath, let me ask you a question. Why did the machine ask you to program in your weight? If you answered to calculate how many calories you burn you are right. What you most likely failed to consider is the main reason it needs your weight is to calculate your basal metabolic rate. The average male will maintain his weight on about 3200 calories a day. That is about 140 calories an hour at rest. So the 300 calories burned are not calories burned above your basal metabolic rate, they are calories burned including your basal metabolic rate. So for your time on the treadmill, you burned about 160 calories above your baseline. If you eat just 3 cookies, you have completely undone about an hour's worth of work. Think about it...if we were so metabolically inefficient as to burn 300 calories at the rate the exercise equipment says you do, would we ever have survived as a species. The calories burned hunting and gathering would have caused us to die of starvation before we could ever have found anything to eat. At that rate of calorie burn, we would barely have enough metabolic economy to survive a trip to the grocery store. Most people have accepted blindly the information displayed on exercise equipment and as such have turned exercise into a form of guilt absolution. Have dessert (600 calories of pie) and feel guilty? Just go to the health club and work on the stepper until 600 calories tick by on the screen. Other than the fact that this simply seems pathetic, it also just doesn't work.
Let us assume that you have the determination and time to do such a workout 7 days a week. If we take the 300 calories burned and subtract out your basal metabolic rate of 140 calories, we are left with 160 calories burned. There are 3,500 calories in a pound of fat. If your appetite is not spurned by the exercise (as it commonly is) and you keep a stable calorie intake, it would take you 21.875 days to burn off a pound of fat with the extra activity. This is assuming that no other variables are present. Unfortunately there is a big variable that almost no-one accounts for...muscle loss. In order to exercise long enough to reach the 300 calorie mark on the stepper or treadmill, you have to perform low intensity steady state activity. Steady state activity does not place much demand on the muscles, that is why it can be carried out for so long. Rather than demanding use of a large percentage of your muscle fibers, you are actually using a small percentage of your weakest, slow-twitch fibers over and over. When you perform this type of exercise your body can adapt by actually losing muscle. Since you use such a small percentage of your muscle mass to do the work, additional muscle is perceived as dead weight, useless and burdensome. If a person persisted in 7 day a week steady state training they could easily lose about 5 pounds of muscle tissue. Muscle tissue is the most metabolically expensive tissue we have; it takes between 50 and 100 calories a day just to keep a pound of muscle alive.