Several months ago, I entered a "Biggest loser" contest at the local World Gym. The contest was 12 weeks long. After 12 weeks, I weighed in at 199 pounds, I had lost over 50 pounds, and yes, I won. :)
It really is simple, and anyone can do it.
You take in less calories than you burn, and you will lose weight. Take in more than you burn and you will gain weight.
I ate small portions several times during the day and did 30 to 60 minutes of cardio each day.
The contest is over, and I am no longer concerned with losing weight. I still am interested in remaining healthy and reducing my body fat while increasing lean muscle, and have modified my eating and exercise habits to help me achieve my new goal.
If those actors in "300" can do it, why can't I? :P