text: how does a teenager know what kind of diet to go on if they are overweight? i am overwieght and i need guidence to lose my excess weight. i don't know what to eat...how to excerise properly or anything. the only way you can know what is good for you is to test them out.  what works for others may not always work for you.  dieting in itself is not a permanent weight management tool.  you need to make a lifestyle change.