As a computer nerd who lived with a body builder in college let me put this into perspective.
1.) If you eat a lot of food, or if you eat food with a lot of fat in it, then you gain weight.
2.) Losing weight requires a fundamental rethinking of your lifestyle.
3.) If you start doing push-ups, sit-ups and running daily but don't change your lifestyle then you will probably put on additional weight (muscle weighs more than fat).
To lose weight you just need a healthy simple plan. Change the types of food you eat and cut calories, then take three days a week to begin working out. I personally lost 55 pounds in 12 months because I was dedicated to the process of getting into shape.