“Dan was 19 when he was hospitalized for schizophrenia. He was prescribed fistfuls of daily medication and, as a side effect, quickly packed on 100 pounds. His treatment and weight remained largely unchanged for more than a dozen years before he slowly began taking steps toward recovery. He took up karate five years ago, getting regular exercise. Then, his doctor prescribed a new diet: He helped Dan cut out nearly all carbohydrates, replacing them with healthy fats and some extra protein. ... The diet is part of a growing trend in medicine: prescribing certain foods — or telling patients to eliminate them — to improve health.”