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'Healthy' obese patients still have higher risk of heart disease

'Metabolically healthy' obese women had 39% higher risk

Adrian O'Dowd

Thursday, 31 May 2018

Women who are obese but classed as "metabolically healthy” still have a higher risk of cardiovascular disease, suggests an observational study* published today in The Lancet Diabetes & Endocrinology journal.

The findings indicate that obesity is a risk factor for cardiovascular disease, regardless of whether or not women develop any of the common metabolic diseases such as high blood pressure or type 2 diabetes.

Obesity (BMI of more than 30kg/m²) affects almost all of the cardiovascular disease risk factors, particularly those related to metabolic syndrome including high blood pressure, poor blood sugar control or diabetes, and abnormal blood fats, which double the risk of cardiovascular disease such as heart attacks and stroke.

However, some people with obesity seem to be free of these metabolic abnormalities and it is estimated that as many as a third of obese people might be "metabolically healthy”.

Whether this so-called “metabolically healthy obesity" is associated with a higher risk of cardiovascular disease has been debated for many years, but it remains unclear how changes or maintenance of metabolic status affect the development of cardiovascular disease in both normal weight and overweight/obese individuals.

Therefore, a team of researchers led by Professor Matthias Schulze from the German Institute of Human Nutrition, Potsdam-Rehbruecke, Nuthetal, Germany, examined the association between obesity and cardiovascular disease incidence in 90,257 women (initially free from cardiovascular disease) from the Nurses’ Health Study – a study tracking the health of female nurses (aged 30-55 years) in the USA since 1976.

Participants were divided into groups by BMI category, metabolic health (defined as the absence of three metabolic risk factors – type 2 diabetes, high blood pressure, and high blood cholesterol), and change in metabolic health status, and followed for 30 years between 1980 and 2010.

Participants were sent questionnaires every two years to update their BMI and metabolic health status, as well as to assess their lifestyle, health behaviour, and medical history.

The researchers took into account a range of factors that may have influenced the results including age, diet, smoking status, physical activity, alcohol consumption, ethnicity or race, highest education level, menopausal status, aspirin use, and family history of heart attack or diabetes.

During an average follow-up of 24 years, there were 6,306 new cases of cardiovascular disease, including heart attacks and strokes recorded.

Cardiovascular disease risk was especially high in all metabolically unhealthy women, regardless of their BMI.

Results showed that metabolically unhealthy normal weight women were around 2.5 times more likely to develop cardiovascular disease compared to normal weight women with no metabolic abnormalities, whilst those with “metabolically healthy obesity" were also at a 39% higher risk of cardiovascular disease.

Importantly, the majority of women who were initially "metabolically healthy" obese (84%), and around two-thirds (68%) of normal weight metabolically healthy women, converted to unhealthy types over 20 years.

Furthermore, even women who maintained "metabolically healthy obesity" over 20 years still had a 57% higher risk of developing cardiovascular disease compared with normal weight metabolically healthy women.

Professor Schulze said: “Our large cohort 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.

“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, putting them at much higher risk for cardiovascular disease.”

*Eckel, N; Li, Y; Kuxhaus, O; Stefan, N; Hu, F; and Schulze, M. Transition from metabolic healthy to unhealthy phenotypes and association with cardiovascular disease risk across BMI categories in 90 257 women (the Nurses' Health Study): 30 year follow-up from a prospective cohort study. The Lancet Diabetes & Endocrinology. DOI:10.1016/S2213-8587(18)30137-2.

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