BOSTON—Having a lower percentage of body fat may not always lower your risk for heart disease and diabetes, according to a study by an international consortium of investigators, including two scientists from the Institute for Aging Research of Hebrew SeniorLife, an affiliate of Harvard Medical School (HMS). The Institute researchers, Douglas P. Kiel, M.D., M.P.H., and David Karasik, Ph.D., who are working with the Framingham Heart Study, identified a gene that is linked with having less body fat, but also with an increased risk of type 2 diabetes and heart disease, examples of so-called "metabolic diseases." "We've uncovered a truly...