What ADHD medications cause loss of appetite?

Most do not cause weight gain. A primary concern for ADHD medicines, actually, is weight loss. Many medicines suppress one's appetite resulting in eating less. They are also many other negative side effects, such as moodiness, insomnia, etc. Do not self-medicate. Discuss with your doctor of which medicine is right for you. (I personally think Concerta is the best, but different medicines work differently for different people.)