A large international study that included Harvard researchers links a high body mass index (BMI)-a calculation used to determine if a person is overweight-to a risk of early death, and contradicts the idea that it's possible to be fat and fit. Researchers pooled the data from 239 studies of more than 10 million people in 32 countries. They excluded people who had smoked, had a chronic condition, or died within five years of follow-up, leaving about four million people. Of those, researchers analyzed people's BMIs. A healthy BMI is considered to be in the range from 18.5 to 24.9. Researchers observed that study participants with a BMI of 20 to 24.9 were the least likely to die during the study period; people with a BMI above or below that were significantly more likely to die during the study period, especially men with high BMIs. The findings, published Aug. 20, 2016, in The Lancet, don't prove that high or low BMIs cause early death, but they do suggest being overweight matters. The bottom line: Extra fat puts you at risk for developing diabetes, heart disease, and cancer, so make weight control a priority.