People with too much fat around their midsections and vital organs are at increased risk for heart disease, even if their body mass index falls within what is considered a healthy range, according to a new scientific report.
The statement from the American Heart Association, published Thursday in its journal Circulation, summarizes research on the ways in which belly fat and other measures of obesity affect heart health. Belly fat also is referred to as abdominal fat and visceral adipose tissue, or VAT.
"Studies that have examined the relationship between abdominal fat and cardiovascular outcomes confirm that visceral fat is a clear health hazard," writing committee chair Dr. Tiffany Powell-Wiley said in a news release. Powell-Wiley is chief of the Social Determinants of Obesity and Cardiovascular Risk Laboratory at the National Heart, Lung, and Blood Institute in Bethesda, Maryland.
Whether a person has too much belly fat is typically determined using the ratio of waist circumference to height (taking body size into account) or waist-to-hip ratio. This measurement has been shown to predict cardiovascular death independent of BMI, a measure of obesity that is based on height and weight.
Experts recommend both abdominal measurement and BMI be considered during regular health care visits because even in healthy weight individuals, it could mean an increased heart disease risk. 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.
Worldwide, around 3 billion people are overweight or have obesity. The "obesity epidemic contributes significantly" to many chronic health conditions and cardiovascular disease cases around the world, Powell-Wiley said. Specifically, obesity is associated with a higher risk of coronary artery disease and death from cardiovascular disease. It contributes to high cholesterol, Type 2 diabetes, high blood pressure and sleep disorders.
Yet some people whose BMI classifies them as obese, but who have low levels of abdominal fat, are at lower risk for heart problems, the analysis showed.
Meeting federal guidelines for 150 minutes of physical activity per week may be sufficient to reduce abdominal fat, the analysis found, with no additional loss from longer activity times. Exercise alone or in combination with diet changes have been shown in some instances to reduce abdominal obesity even without weight loss.
Also, weight loss from lifestyle changes improves blood sugar, blood pressure, and triglyceride and cholesterol levels – a cluster of factors referred to as metabolic syndrome, according to the new statement. It also reduces inflammation, improves blood vessel function and helps non-alcoholic fatty liver disease.
In addition, intense weight loss may help curb atrial fibrillation, a quivering or irregular heartbeat, according to the report. Estimates suggest obesity may account for one-fifth of all cases.
The new scientific statement evaluated research on managing and treating obesity, particularly abdominal obesity. Experts concluded that reducing calories and aerobic exercise were the most beneficial.
Bariatric weight loss surgery has been shown to reduce the risk for coronary artery disease better than weight loss achieved without surgery. This may be due to the larger amount of weight loss achieved with surgery and the resultant changes in metabolism that are typical after bariatric surgery.
The statement also addresses what's known as the "obesity paradox." That is, even though overweight and obesity are strong risk factors for cardiovascular disease, in the short-term, they don't always mean patients have worse survival outcomes. The analysis concludes this may be because people classified as overweight or obese are often screened earlier for cardiovascular disease than people with healthy weight, so they are diagnosed and treated earlier.
"The underlying mechanisms for the obesity paradox remain unclear," Powell-Wiley said. "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."
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