Research has suggested that excess weight around the midsection of a person's body is a better predictor of poor heart health than body-mass index (BMI) measurements. A new report has indicated that even when a person's BMI is within a range that's considered healthy, abdominal obesity increases the risk of heart disease. The findings have been published in a Scientific Statement by the American Heart Association in their 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, chief of the Social Determinants of Obesity and Cardiovascular Risk Laboratory at the National Heart, Lung, and Blood Institute, among other appointments. "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."
Excess weight around the abdomen, sometimes called visceral adipose tissue or VAT, can be determined in several ways, including by measuring the waist-to-hip ratio or waist circumference. VAT can act as a biomarker of cardiovascular death regardless of BMI. It's recommended that VAT and BMI should be assessed during checkups. People in a healthy weight range may be at greater risk of heart disease if they have a high waist circumference or low waist to hip ratio. Abdominal obesity has also been associated with non-alcoholic fatty liver disease.
"Studies that have examined the relationship between abdominal fat and cardiovascular outcomes confirm that visceral fat is a clear health hazard," noted Powell-Wiley.
Abdominal obesity is such a strong indicator of poor health, if people have a BMI in the obesity range but low fat levels around the abdomen, it seems to lower their risk of cardiovascular disease in a concept known as metabolically healthy obesity.
In the “obesity paradox,” people that fall into the overweight or Class I obesity (BMI = 30 to 34.9 kg/m2) category are not always at greater risk for poor cardiovascular health, although overweight and obesity are major risk factors for cardiovascular disease development. But, the study authors noted that people in those categories might be screened earlier for cardiovascular disease than healthy-weight individuals, so they may get a diagnosis and treatment earlier.
“The underlying mechanisms for the obesity paradox remain unclear,” said Powell-Wiley. “Despite the existence of the paradox for short-term cardiovascular disease outcomes, the data show that patients with overweight or obesity suffer from cardiovascular disease events at an earlier age, live with cardiovascular disease for more of their lives, and have a shorter average lifespan than patients with normal weight.”
In this study, the researchers found that if people can meet the recommendation of 150 minutes of physical activity per week, they can reduce abdominal fat levels. Longer activity times do not seem to reduce it more. There is some evidence that exercise or a combination of diet changes and physical activity can lower reduce abdominal obesity without overall weight loss.
While lifestyle changes that reduce weight in obese individuals can improve biomarkers like blood sugar, cholesterol levels, and triglycerides, reduce inflammation, and treat non-alcoholic fatty liver disease, there is no evidence that these changes lower heart attack or chest pain levels in those individuals. However, bariatric surgery for weight loss has been linked to a reduction in the risk of coronary artery disease compared to non-surgical weight loss. This difference may be due to the degree and timetable of weight loss and metabolic changes.
"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 researchers suggested that there is also now enough convincing data that obesity is increasing the risk of atrial fibrillation. They estimated that as many as 20 percent of atrial fibrillation cases are caused by obesity. People with atrial fibrillation who lost a lot of weight have been able to improve their symptoms.
"The research provides strong evidence that weight management be included as an essential aspect of managing atrial fibrillation, in addition to the standard treatments to control heart rate, rhythm and clotting risk," said Powell-Wiley.
Sources: AAAS/Eurekalert! via American Heart Association, Circulation
