Excerpt: More than a quarter of the phenomenal growth in health care spending over the past 15 years is attributable to obesity, Emory University researchers reported yesterday. With 60 percent of the U.S. population deemed overweight or obese, study author Kenneth Thorpe said the only way to control soaring medical costs is to begin targeting prevention efforts and treatment on the most costly weight-related illnesses, such as diabetes, high cholesterol and heart disease.