Extreme Obesity can Reduce Lifespan by 14 Years: NIH Study

Obesity is a serious chronic condition that can lead to several health complications such as heart disease, diabetes and even some kinds of cancer. A third of the world's population is either overweight or obese, making obesity a public health risk factor.

Now, researchers at the National Cancer Institute (NCI) and colleagues have found that class III obesity or a BMI of 40 or over could shorten life expectancy.

"While once a relatively uncommon condition, the prevalence of class III, or extreme, obesity is on the rise. In the United States, for example, six percent of adults are now classified as extremely obese, which, for a person of average height, is more than 100 pounds over the recommended range for normal weight," said Cari Kitahara, Ph.D., Division of Cancer Epidemiology and Genetics, NCI, and lead author of the study, according to a news release. "Prior to our study, little had been known about the risk of premature death associated with extreme obesity."

The study was based on data from 20 studies conducted in three countries: United States, Sweden and Australia. Researchers evaluated early death risk in over 9,500 individuals who were classified as extremely obese and 304,000 others who were classified as normal weight. Premature death risk was assessed for both specific cause such as cancer or heart disease and even overall risk.

Researchers found that heart disease, cancer and diabetes were the major causes of early death in class III obese people. Participants of BMI of 40-44.9 were more likely to lose around 6 years of their life, while those with BMI of 55-59.9 had a reduction in life expectancy by as much as 13.7 years .

To put the numbers in perspective, the number of years lost by people who smoke tobacco as compared to non-smokers is same as obese people lose. 

Note that participants in the study were all non-smokers and didn't have a history of other diseases.

Major limitations of the study include the use of BMI as a sole measurement for obesity, researchers said.

Still, the research shows that extremely obese people have high risk of premature death.

"Given our findings, it appears that class III obesity is increasing and may soon emerge as a major cause of early death in this and other countries worldwide," said Patricia Hartge, Sc.D., Division of Cancer Epidemiology and Genetics, and senior author of the study.