@Mor - That's not enough for some people though. And I think when people are learning to eat well, it helps to know portion sizes and how many calories are in everything, because they are often surprised how many calories are in things they took for granted.
Heck, even fruit can have quite a few calories if you eat too much of it. Meat can have quite a few as well, particularly when it is eaten in bulk.
I know when I started a diet and thought I would be clever and fill up on steak rather than on biscuits, I was dismayed to find out that I was actually still eating about the same amount of calories, even with lean meat.
Of course, the steak keeps you full for longer, so it has other benefits in the long run.