The findings, published in The Lancet Diabetes and Endocrinology journal, indicate that obesity, even if considered 'metabolically healthy' is a risk factor for cardiovascular disease, regardless of whether or not women develop any of the common metabolic diseases.

Obesity affects almost all of the cardiovascular disease risk factors. However, some people with obesity seem to be free of these and might be metabolically healthy. Women who are obese and who have been metabolically healthy for decades are still at higher risk of developing cardiovascular disease compared to metabolically healthy women of normal weight, according to a study of over 90,000 women.

Obesity affects people with metabolic syndrome including high blood pressure, poor blood sugar control, and abnormal blood fats, and double the risk of cardiovascular disease such as heart attacks and stroke. However, some people with obesity seem to be free of these abnormalities and might be metabolically healthy, casting doubt on whether or not the excess weight actually raises their risk.

In the study women with "metabolically healthy obesity" were also found to be at 39 per cent higher risk of cardiovascular disease. Women with normal weight but metabolically unhealthy were around two-and-a-half times more likely to develop cardiovascular disease than women of the same weight who were metabolically healthy.

"Our study confirms that 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 Matthias Schulze, Professor at the German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE) in Nuthetal, Germany.

"Most healthy women are also 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 added. For the study, the team examined the association between obesity and cardiovascular disease incidence in 90,257 women. Importantly, the majority of women who were initially metabolically healthy obese and of normal weight converted to unhealthy phenotypes over 20 years.

"Our findings highlight the importance of preventing the development of metabolic diseases, and suggest that even individuals in good metabolic health may benefit from early behavioural management to improve their diet and increase physical activity in order to guard against progression to poor metabolic health," Schulze said.