Women who are obese face an increased risk of cardiovascular disease, even if they have maintained good metabolic health - free of type 2 diabetes, high blood pressure and cholesterol - for decades, a study has found.
The 30-year study of 90000 American women, published in the journal The Lancet Diabetes & Endocrinology, is another to pour cold water over the myth that people can be obese and still healthy, or 'fat but fit'.
"Our large cohort study confirms metabolically healthy obesity is not a harmless condition, and even women who remain free of metabolic diseases for decades face an increased risk of cardiovascular events," said lead author, Professor Matthias Schulze, of the German Institute of Human Nutrition.
"What's more, we observed that most healthy women are likely to develop type 2 diabetes, high blood pressure, or high cholesterol over time, irrespective of their BMI (body mass index), putting them at much higher risk for cardiovascular disease," he said.
Obesity has been linked to all of the cardiovascular disease risk factors; high blood pressure, poor blood sugar control or diabetes, and abnormal blood fats (high cholesterol).
These can double the risk of heart attacks and stroke.
However, previous research suggests as many as a third of obese people seem to be free of these metabolic abnormalities, what doctors have coined 'metabolically healthy'.
To investigate this further, researchers examined the association between obesity and cardiovascular disease incidence in 90257 women from the Nurses' Health Study - a study tracking the health of female nurses (aged 30-55 years) in the USA since 1976.
Participants were sent questionnaires every two years to update their BMI and metabolic health status.
During an average follow-up of 24 years, there were more than 6300 new cases of cardiovascular disease, including 3304 heart attacks and 3080 strokes were recorded.
Cardiovascular disease risk was especially high in all metabolically unhealthy women, regardless of their weight.
They were around 2.5 times more likely to develop cardiovascular disease compared to normal weight women with no metabolic abnormalities, while those with 'metabolically healthy obesity' were also at a 39 per cent higher risk of cardiovascular disease.
Even women who maintained metabolically healthy obesity over 20 years still had a 57 per cent higher risk of developing cardiovascular disease compared with normal weight metabolically healthy women.