Obesity rates in the United States have doubled in the past 20 years and without changes, nearly half of the adult population will be obese by 2030. Though there are many approaches to weight loss—diet and exercise, drugs, surgery—their safety and efficacy varies widely from patient to patient. Phenomix Sciences is using phenotyping to understand the type of obesity each individual has to tailor treatments that address it specifically. Based on work at the Mayo Clinic, Phenomix breaks obesity into four different subtypes. We spoke to Mark Bagnall, CEO of Phenomix, about the company’s efforts to bring precision medicine to the treatment of obesity, the testing it performs, and the science underlying its approach.