What's a good plan for long term weight loss in a 19 year old?

Diet/exercise. You need to get a good exercise program 3-4 times a week and change your diet with high protein, low fat, low carbohydrate.
Exercise/diet. Long term plan for young pt should be a regular exercise 3-4 times a week plus a good diet program with high protein, low fat, and low carbohydrate.