The five-year long research conducted by the Canadian medical researchers, led by Dr Joel Ray has concluded that being underweight is even riskier than being overweight or obese.
He found that adults who are underweight – with a BMI under 18.5 or less – have a 1.8 times higher risk of dying than those with a “normal” BMI of 18.5 to 24.9.
The risk of dying is 1.2 times higher for people who are obese (BMI of 30-34.9) and 1.3 times higher for those who are severely obese (a BMI of 35 or higher).
The researchers required that studies follow people for five years or longer, to weed out those who were underweight simply because of cancer or chronic lung disease or heart failure. Common causes of being underweight include malnourishment, heavy alcohol or drug use, smoking, low-income status, mental health or poor self-care.
The study has been published in the Journal of Epidemiology and Public Health.