You should all read "Eat, Drink & Be Healthy" by Walter C. Willett, M.D.
Being healthy is about a lifestyle, there are no shortcuts. As many have said earlier, if calories in < calories burned weight goes down. But you also must maintain a well balanced diet to be healthy. Willett's book is based on many long term studies and does not offer to have all of the answers, just the best that they can come up with today.
Now if I could just get out of this chair and to the Gym for an hour . . . you would think an hour is not that much time . . . but I seem to never be able to find that "hour"
(This guy is encouraging us all to exercise!)