By doing exercise, and eating healthy. You will have to burn 87500 calories to lose 25 pounds (3500lbs per pound). Aim for weight loss of 1-2lb per week, although you may lose more in the beginning....
Just try to excersize daily but you can still eat junk food just in small portions. And jog for about 20 minutes after eating. Or try doing something fun like playing wii fit try the biking game my...