Investigation of the effect of a single dose of stimulant medication (dexamphetamine 10mg or methylphenidate 20mg) on appetite and on fasting and postprandial levels of insulin, glucose, leptin and ghrelin in healthy adult volunteers.

This study is for healthy young adults and looks at how a single dose of stimulant medication (dexamphetamine or methylphenidate — the type used to treat ADHD in children) affects appetite and hormone levels in the blood. Stimulant medications can slow growth in children, possibly by reducing hunger. This study will measure levels of hormones like leptin and ghrelin (which control appetite) before and after a meal, when on the medication versus a dummy pill. The results will help us understand how these medications affect the body. You may be eligible if: - You are between 17 and 30 years old - You are fit and healthy You may NOT be eligible if: - You are currently being treated for any medical condition - You have previously used stimulant medication regularly - You have a history of substance abuse - Your BMI is over 30 Talk to your doctor about whether this trial might be right for you.