A new study in The Lancet suggests that without intervention, U.S. obesity rates will increase dramatically in the coming decades. By 2030, as many as 164 million Americans could be obese. In that time, the obesity rate for men is projected to rise from 32 percent to 50 percent and from 35 percent to 45-52 percent for women. Health care costs related to conditions such as type 2 diabetes, heart disease and cancer would also rise.