In a study published this week in the British medical journal The Lancet, Oxford University researchers have determined that severely obese people (those with a BMI of 40 or higher) shorten their life spans by up to a decade, which is as life-shortening as being a smoker. Those who are moderately obese (BMI of 30-35) can shorten their life spans by 3 years.
This was no small study: A million people were followed for 20 years to collect information.
One encouraging takeaway from the study: The best BMI to have, the researchers found, is about 24 -- the group with the lowest morality rate. A BMI of 25 is considered overweight, so the study shows that it's better to be at a healthy weight instead of "skinny."
Need to figure your BMI? Do it here