Body Mass Index and Mortality in a Very Large Cohort: Is It Really Healthier to Be Overweight?

Controversy persists about optimal body weight. Many experts define “normal” (healthy) body mass index (BMI) as 18.5 to 24.9 kg/m2, 25 to 29.9 kg/m2 as overweight, and 30 kg/m2 or greater as obese. Obesity is subdivided into 30 to 34.9 kg/m2 (Grade 1), 35 to 39.9 kg/m2 (Grade 2), and 40 kg/m2 and above (Grade 3). Studies consistently show higher mortality for underweight and Grade 2 or 3 obesity, but results conflict for the overweight category and Grade 1 obesity