In a surprising study published by PLOS Medicine, researchers have found that normal weight smokers have a longer life span than obese non-smokers.

The study emphasizes the immense side effects that obesity can have on the human lifespan. Heart disease, strokes, diabetes and other weight causes aliments can all contribute to a shorter lifespan.

According to the Center for Disease Control and Prevention, more than 35 percent of Americans are now classified as obese.

Obesity is defined as having a BMI over 30, while overweight is defined as having a BMI of 25.0 to 29.9. The study looked at those who are classified as extremely obese which comes with a BMI of over 40.

The research project took 20 prospective studies from the U.S., Australia and Sweden and combined the information to gather their totals.

The scale of the project was more than 9,500 extremely obese adults and more than 300,000 normal weighing adults.       

When comparing the lifespans between extremely obese and normal weight adults, researchers found that obese individuals die an average of 6.5 to 13.7 years earlier than their normal weight counterparts.

Normal weight non-smoking adults live an average of 8.9 years longer than a smoking normal weight adult.

The real difference comes into the extremely obese adults in comparison to normal weight smoking adults. Extremely obese adults with a BMI of 50.0 to 55.0, die on average 6 years earlier than smoking normal weight adults.

Project researchers wrote, "These results have great relevance to the current era, during which class III obesity rates have increased dramatically at the same time that smoking rates have declined."

"Before we can prevent and treat class III obesity effectively, we need a better understanding of the health risks associated with this condition,"  according to the report.