Don't smoke
wear sunblock
eat healthy
You want to be able to treat the disorder before it gets too bad and irreparable. If you figure out whats going on and what food or substances are causing the issue, you can avoid those and take other precaustions as well.
Answer:
Lose weight: To lose weight, caloric input needs to decrease, and caloric output needs to increase?
Gain weight: To gain weight, caloric input needs to increase, and caloric output needs to decrease.
Keep your back straight and knees bent
