A 32-year-old man with a past medical history of depression and schizophrenia presents to your clinic for a routine follow-up appointment. Six months ago, he was prescribed olanzapine for management of his schizophrenia and has since had a 10 kg increase in weight. He states that he is concerned about the weight gain as his father was "overweight and died of a heart attack in his 40s." Which medication would be most appropriate for this patient?