M.L.
Do you know what a calorie is? It's a measurement of energy in a food substance. You have to have enough of them for the energy to excersize. You have to excersize to help your heart and to tone, which is why you need calories if you aer excersizing. Just not eating calories won't give you all the benefits that you need by excersizing.... so even if you reduce your caloric intake of bad foods, you still need to have an active life.
Also, there are things as "empty calories". All foods have calories, some "empty" like sugars and unhealthy foods. Empty calories you want to avoid. They fill you up, but your stomach has nutrition 'detectors". You may have a full stomach, but your stomach is sill hungry b/c it isn't full of nutrient, so it tells your brain to eat more, in hopes that it will get something of substance.
So, instead of just calorie counting (most reputable dieticians/nutritionists advise to avoid this), so they ask you to focus on the QUALITY and portion size of food as well as trying to stay on caloric goal. So, if you are making homemade soup, reduce sodium content, don't use "cream of condensed soups" b/c they are also full of unnecessary preservatives and such. Use fresh or frozen veggies instead of canned for the same reason, and also b/c they are higher in nutritional value.
Okay, so these sites explain it a lot better!:
http://www.superkidsnutrition.com/nutrition_answers/nw_wh...
http://health.howstuffworks.com/wellness/diet-fitness/wei...