NEW YORK (Reuters Health) - With a body mass index (BMI) of 30 or higher - the definition of obesity - median survival is reduced by 2 to 10 years, according to a new report.

Also, a BMI below 22.5 -- the definition of underweight -- is also associated with higher mortality rates, due primarily to smoking-related diseases, the report in The Lancet medical journal indicates.

BMI is the standard measure of weight in relation to height. It is calculated by dividing weight in kilograms squared ...