People with abdominal obesity and excess fat around the body's midsection and organs have an increased risk of heart disease even if their body mass index (BMI) measurement is within a healthy weight range, according to a new scientific statement. The statement was issued by the American Heart Association this week in the Association's flagship journal, ‘Circulation’.
"This scientific statement provides the most recent research and information on the relationship between obesity and obesity treatment in coronary heart disease, heart failure and arrhythmias," said Tiffany M. Powell-Wiley, M.D., M.P.H., FAHA, chair of the writing committee and a Stadtman Tenure-Track Investigator and chief of the Social Determinants of Obesity and Cardiovascular Risk Laboratory in the Division of Intramural Research at the National Heart, Lung, and Blood Institute at the National Institutes of Health in Bethesda, Maryland.
"The timing of this information is important because the obesity epidemic contributes significantly to the global burden of cardiovascular disease and numerous chronic health conditions that also impact heart disease," added Powell-Wiley.
A greater understanding of obesity and its impact on cardiovascular health highlights abdominal obesity, sometimes referred to as visceral adipose tissue, or VAT, as a cardiovascular disease risk marker. VAT is commonly determined by waist circumference, the ratio of waist circumference to height (taking body size into account) or waist-to-hip ratio, which has been shown to predict cardiovascular death independent of BMI.
Experts recommend both abdominal measurement and BMI be assessed during regular health care visits because a high waist circumference or low waist-to-hip ratio, even in healthy weight individuals, could mean an increased risk of . Abdominal obesity is also linked to fat accumulation around the liver that often leads to non-alcoholic fatty liver disease, which adds to cardiovascular disease risk.
"Studies that have examined the relationship between abdominal fat and cardiovascular outcomes confirm that visceral fat is a clear health hazard," said Powell-Wiley.
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The risk-inducing power of abdominal obesity is so strong that in people who are overweight or have obesity based on BMI, low levels of fat tissue around their midsection and organs could still indicate lower cardiovascular disease risks. This concept, referred to as "metabolically healthy obesity," seems to differ depending on race/ethnicity and sex.
Worldwide, around 3 billion people are overweight (BMI = 25 to 29.9 kg/m2) or have obesity obese(BMI ?30 kg/m2). Obesity is a complex disease related to many factors, including biological, psychological, environmental and societal aspects, all of which may contribute to a person's risk for obesity.
Obesity is associated with a greater risk of coronary artery disease and death due to cardiovascular disease and contributes to many cardiovascular risk factors and other health conditions, including dyslipidemia (high ), type 2 diabetes, high blood pressure and sleep disorders.
For this statement, experts evaluated research on managing and treating obesity, particularly abdominal obesity. The writing group reports that reducing calories can reduce abdominal fat, and the most beneficial physical activity to reduce abdominal obesity is aerobic exercise. Their analysis found that meeting the current recommendations of 150 min/week of physical activity may be sufficient to reduce abdominal fat, with no additional loss from longer activity times. Exercise or a combination of dietary change and physical activity has been shown in some instances to reduce abdominal obesity even without weight loss.
Lifestyle changes and subsequent weight loss improve blood sugar, blood pressure, triglyceride and cholesterol levels – a cluster of factors referred to as metabolic syndrome - and reduce inflammation, improve blood vessel function and treat non-alcoholic fatty liver disease. However, studies of lifestyle change programs have not shown a reduction in coronary artery disease events (such as or chest pain).
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In contrast, bariatric surgery for weight loss treatment is associated with a reduction in coronary artery disease risk compared to non-surgical weight loss. This difference may be attributed to the larger amount of weight loss and the resultant changes in metabolism that are typical after bariatric surgery.
"Additional work is needed to identify effective interventions for patients with obesity that improve cardiovascular disease outcomes and reduce cardiovascular disease mortality, as is seen with bariatric surgery," said Powell-Wiley.
The statement also addresses the "obesity paradox," which is sometimes observed in research, particularly in populations that have overweight or have Class I obesity (BMI = 30 to 34.9 kg/m2).
The paradox suggests that even though overweight and obesity are strong risk factors for the development of cardiovascular disease, they are not always a risk factor for negative cardiovascular outcomes. The writing group notes that people with are often screened earlier for cardiovascular disease than people with healthy weight, thus resulting in earlier diagnoses and treatment.