Maybe you file this topic under “obvious,” but common wisdom has been mistaken before. In fact, some research suggests there is no relationship between weight and mortality.

Researchers from The Global BMI Mortality Collaboration believed the weight/mortality issue needed more scrutiny. They published new research in the July 13 issue of The Lancet. The results are stunning.

The previous research looked at Body Mass Index (BMI) and its relationship to mortality. BMI is an index that correlates weight with height as a way to define what is underweight, normal, overweight and obese. The previous research found no relationship between BMI and mortality. But it also didn’t account for the effect of smoking and chronic disease. These factors can affect both weight and mortality. With the latest research, these factors were accounted for.

Researchers reviewed 239 prospective studies on BMI with 10,625,411 participants. They excluded those who smoked or had chronic disease. They also excluded those who died in the first five years. This eliminated the possibility that smoking or existing disease caused the deaths. Of the remaining 3,951,455 individuals from four continents, 385,879 died after the initial five-year period.

Researchers used a BMI of 20 to 25 to compare other subgroup results. This range is commonly considered “normal” weight. Their findings are as follows:

Correlation of BMI with All-Cause Mortality

Correlation of BMI with All-Cause Mortality

Call it The Bell Curve of Death. The results couldn’t be clearer. The further you are from normal weight, the greater the mortality impact. Overweight and underweight are associated with increased all-cause mortality.

Sadly, here in the U.S., the population skews heavily toward the right of that curve. Only 31.2 percent have a BMI under 25 with a small 1.7 percent in the underweight category. Another 35.7 percent have a BMI in the 25.0-30.0 “overweight” range, and 33.1 percent are classified as obese or extremely obese with a BMI over 30.0. The bulk of us have a significantly increased chance of dying because of our BMI. And while the U.S. houses five percent of the global population, it is responsible for one-third worldwide excess weight.

Each additional point of BMI translates to additional healthcare costs. Researchers at Duke University studied the health insurance claims of over 17,000 employees from 2001 to 2011. They found that an individual with a BMI of 19 had an average annual healthcare cost of $2368. This number grew steadily with BMI, reaching $4,880 per year for those with a BMI of over 45.

And here’s a fun fact. The U.S. accounts for five percent of the world’s population, but is responsible for one-third of global excess weight. May that has something to do with why our healthcare costs are the highest in the world.

There are a couple of caveats that should be mentioned here. BMI is an imperfect measurement. It doesn’t account for muscle mass vs. fat mass in the calculation. So a muscular person is going to have a higher BMI and that isn’t necessarily a bad thing. This means it isn’t the best marker for an individual, but on a population level, it gives us excellent information.

In addition, these ranges aren’t tiny. I’m 5’4” and my weight range to be considered “normal” weight is 108 to 145. Not everyone has to fit into their high school jeans to be considered normal weight. It’s simply not that last ten pounds causing the problem.

Even so, it’s clear from this research that the relationship between BMI and mortality is real. With two-thirds of us in the U.S. falling in the overweight or obese column, it’s critical that we take this seriously. On a personal level it can mean additional years of healthy living. On a national scale, it can mean billions of healthcare dollars saved.