Because it's more how you eat. Optimally you should eat a small meal every 2-3 hours to keep your metabolism up. Most people simply eat 2 to 3 large meals throughout the day.
You'd be amazed how much you can eat and not gain weight after a month or so of doing this. I was eating around 3,000 calories per day and still losing pretty quickly by doing this. But it was all still relatively healthy foods.