Swedish researchers have found that obesity might not increase the risk of heart attack or premature death, in a finding that goes against accepted belief.
In the study which involved identical twins, researchers looked at cases where one twin was overweight or obese and the other was trimmer.
"The heavier twin had a lower risk of heart attack or death than the leaner twin. However, as expected, the heavier twin had a higher risk of diabetes," said lead researcher Peter Nordstrom, chief physician in the department of community medicine and rehabilitation at Umea University.
"Lifestyle factors that decrease the amount of fatness may not reduce the risk of cardiovascular disease or death, although it will reduce the risk of [type 2] diabetes," Nordstrom added.
He added, as identical twins were genetically the same, they provided a unique tool for evaluating risks associated with obesity independent of genetics.
According to the US Centers for Disease Control and Prevention, obesity was linked to heart disease, stroke, type 2 diabetes and certain types of cancer.
According to the CDC, obesity-related illness cost the US about $147 billion annually.
Around 5 per cent of the twins in the study group reported a heart attack during 12 years of follow-up.
Among twins with lower BMI, about 16 per cent died as against 14 per cent of twins with higher BMI. However, heavier twins were around twice as likely to develop diabetes over the study's length.
"What the study does show is that there's a strong association between obesity and diabetes, which leads us to conclude that weight reduction interventions can be more effective against diabetes than when it comes to reducing the risk of heart attack and mortality," said Nordström in a statement.
Researchers looked at medical records of more than 4,000 identical twin pairs previously enrolled in a long-running population study. The middle-aged pairs who were tracked for 12 years, had one twin with a higher body mass index (BMI) than the other.
The researchers were surprised to find no noticeable difference in the rate of heart attacks or premature death between the group of twins with higher BMI and the group with lower BMI, even when only obese individuals or twin pairs where the weight difference were considered.
They did find a sustained link between Type 2 diabetes risk and higher BMI which supported earlier research.