Obesity is linked to many serious health complications, including type 2 diabetes, heart disease, some cancers, kidney disease and mental health issues. Now, a study projects that nearly half of the U.S. population – about 126 million people 20 and older – will have obesity by 2035. These figures were lower than findings from other research that used a definition of obesity that goes beyond body mass index. That study, and the one published Wednesday, used the standard definition of obesity as having a BMI of 30 or higher. But the researchers noted limitations of the study, including the definition of obesity based solely on BMI.