Sixteen year old girl wanting to lose weight?

Eat less move more: Assuming she is either overweight or obese - weight loss would be appropriate. She would do it in the same way as adults - eat less and move more. Track her dietary intake, eliminate sugar beverages and high fat foods. Increase exercise - ideally 1 hr/ day. If she is already a healthy weight and wants to lose weight - consider counseling as it may be a sign of a mental health problem.