The outcome contrasts with studies for women, who are believed to be more depressed if they are overweight.
“There are many reasons for suicide, but the fact that overweight men are less at risk supports the assumption that there are biological reasons,” researcher Finn Rasmussen at Stockholm’s Karolinska Institute told Swedish radio.
There are many medical problems connected to being overweight, such as high blood pressure, diabetes and clogged arteries, but for men depression is not one of them, Rasmussen said.
He admitted that researchers had no conclusive explanation for the link between the body mass index (BMI) and a lower risk of suicide.
“But we believe that, despite the social discrimination suffered by fat men, there is an underlying biological mechanism that protects them,” he said.
Still Rasmussen warned against fattening up as a remedy against depression “because of the many negative side effects of being overweight”.
The research is based on medical tests conducted on all Swedish men drafted into the military between 1968 and 1999, a total of 1.3 million, who were examined when they were 18 or 19 years old.
Just over 3,000 committed suicide later in life.