I have also wondered how accurate those readouts are...sometimes I can burn as much as eight hundred calories an hour on the eliptical! I do have to put in my two cents here...I don't believe in the whole "a calorie is a calorie" business...the quality of the food is of vital importance to your health and longevity...we are what we eat is pretty literal...why work hard exercising, only to go and eat pizza, chips and ice cream(or whatever form your junk food cravings take)...I say the more you move to a whole foods based diet with an emphasis on vegies(esp.greens), the better you will feel...remember, its not all about how much weight we lose, its about how we feel in our bodies, and ultimately, we will all be saggy someday(God willing we all live that long), but my goal is to feel as good as I can in my body for my entire life!

Two issues:

As you get in better shape, your metabolism changes, and this changes the requirements of your diet. It's not just 1 calorie in = 1 calorie out. Adding muscle mass will require that you increase your intake of calories to maintain balance, but you should still be able to burn fat.

A calorie is not a calorie. Say, for example (because this has happened to me) you're adding muscle mass, and thus have a bigger protein requirement. But you're not eating a lot of protein in most of your foods. This means that you're going to feel "hungry" a lot - your body is screaming "protein" but you're responding with "food that contains little protein."

So you're still hungry! You can actually eat MORE calories and GAIN weight, because you're not addressing your body's nutritional needs, and interpreting a specific request ("feed me more protein") as a general one ("feed more more calories.") A nutritionist friend of mine recommended that I supplement with a protein supplement to help solve the very problem you're describing.

Replacing junk food with better balanced food should help you eat what your body needs while consuming fewer calories. You'll be less hungry. On a bad diet, it's very hard to add muscle while burning fat.

The "calorie counters" on different pieces of exercise machinery are extremely inaccurate. Don't try to use them as a measure against the calories you eat, but rather use them as a baseline to measure how hard you're working out, and to track your workouts. Realize however, that different types of machines (even ones by the same manufacturer focusing on the same exercise) measure calories differently and so the numbers may not be transferable.

It's also important to eat enough while you work out. You can actually do some substantial damage to yourself if you don't feed yourself properly while adjusting your lifestyle to include more exercise.