A three-year-old American girl has been diagnosed with type 2 diabetes — a condition linked to obesity — making her one of the youngest people ever detected with the disease. Type 2 diabetes used to be known as “adult-onset” because it is most common among the middle-aged and elderly, but in the last two decades increasing numbers of children have succumbed, due to poor diets and lack of exercise. Details of the case are being presented on Thursday at the annual meeting of the European Association for the Study of Diabetes in Stockholm by Michael Yafi, director of pediatric endocrinology at the University of Texas, Houston.