Being underweight may be even more deadly than being overweight, according to a recent study HealthDay reported.

Researchers from Li Ka Shing Knowledge Institute of St. Michael's Hospital in Canada contend that people who are clinically underweight face nearly twice the risk of death compared to normal-weight folks, HealthDay reported.

As society aims to curb the obesity epidemic, "we have [an] obligation to ensure that we avoid creating an epidemic of underweight adults and fetuses who are otherwise at the correct weight," study leader Dr. Joel Ray, a physician-researcher at St. Michael's Hospital in Toronto, said in a statement.

For the study, researchers reviewed more than 50 studies. They analyzed studies that followed people for five years or more - to weed out those who were underweight simply because of cancer or chronic lung disease or heart failure - and focused on associations between body-mass index ( BMI)and fatalities related to any cause.

Researchers also looked at how death rates related to weight patterns among newborns and stillbirths.

He found that adults who are underweight - with a BMI lower than 18.5 - have a 1.8 times higher risk of dying than those with a "normal" BMI of 18.5 to 24.9.

By contrast, obese individuals - with a BMI of 30-34.9 - the risk of dying is 1.2 times higher than those with a "normal" BMI.

"BMI reflects not only body fat, but also muscle mass. If we want to continue to use BMI in health care and public health initiatives, we must realize that a robust and healthy individual is someone who has a reasonable amount of body fat and also sufficient bone and muscle," Ray said. "If our focus is more on the ills of excess body fat, then we need to replace BMI with a proper measure, like waist circumference."

Ray said common causes of being underweight include malnourishment, heavy alcohol or drug use, smoking, low-income status, mental health or poor self-care.

The findings were recently published in the Journal of Epidemiology and Public Health.