We know that people who are very fat tend to live shorter life spans. But how much shorter?

According to a new study, obesity cuts 14 years from your life.

Researchers found that people with a body mass index (BMI) of more than 40 are at a substantially greater risk of death from the three major killers — heart disease, cancer, and diabetes — than are normal-weight people.

BMI is a calculation that shows the amount of body fat compared to a person’s weight and height. A person with a BMI of more than 30 is considered obese. The people in the 40 + range are in the category of “very severely obese.”

To better understand the impact of obesity on mortality, researchers analyzed 20 studies, and compared data between 9,564 individuals with BMIs of between 40.0 and 59.09 with 304,011 normal-weight people. Their research was published in the journal PLOS One.

Mortality rates among the most overweight individuals were 566 and 663 deaths per 100,000 in men and women, respectively.

By contrast, mortality rates among normal-weight participants were 346.7 in men and 280.5 in women.