The study was so explosive that an entire Harvard conference was convened to debunk it: research published last year concluding that being mildly obese does not shorten life span, while being slightly overweight actually could lengthen it.

Spearheaded by epidemiologist Katherine Flegal of the Centers for Disease Control’s National Center for Health Statistics (NCHS), the research reviewed 97 weight studies covering almost three million people. It found that overweight people had lower death rates than people whose weight was normal and that mildly obese people didn’t die at greater rates than normal-weight people. Researchers call this counterintuitive conclusion the “obesity paradox.”