Belly Fat Outperforms BMI in Predicting Heart Disease Risk, Major Study Finds
核心洞察
A study of nearly 260,000 adults found waist circumference and waist-to-hip ratio better predict future heart disease risk than body mass index (BMI) alone.
People at a healthy weight or with overweight but high abdominal fat faced a 15% to 50% higher risk of heart attack, stroke (搜索), heart failure (搜索), atrial fibrillation (搜索), and cardiovascular death.
Visceral fat is metabolically active, releasing chemicals that drive inflammation, insulin resistance, and artery damage, independent of overall body weight.
The amount of belly fat a person carries may be a better predictor of future heart disease risk than body mass index (BMI) alone, according to a new study published in the Journal of the American College of Cardiology (JACC) on August 11.
Researchers from the Cross-Cohort Collaboration analyzed health data from nearly 260,000 adults enrolled in 15 long-term health studies, following participants for about 20 years. The study found that some people considered a normal weight based on BMI still carried higher levels of fat around their midsection, and that this abdominal fat was associated with significantly elevated cardiovascular risk.
"BMI only tells us weight relative to height, it doesn't tell us where fat is stored, and that matters," said Erin Palinski-Wade, a New Jersey-based registered dietitian and certified diabetes educator, who was not involved in the study.
Why Waist Measurements Matter
For many years, BMI, calculated from a person's height and weight, has been widely used to assess whether a person's weight may pose health risks. However, measures such as waist circumference and waist-to-hip ratio can provide additional information about body composition and health risks.
"Abdominal fat is the fat distributed within the belly, surrounding the organs of the belly," explained the study's senior author, Michael J. Blaha, MD, MPH, director of the Cardiometabolic Clinic at the Johns Hopkins Ciccarone Center (搜索) for the Prevention of Cardiovascular Disease (搜索). "This fat depot is called visceral fat because it is within the viscera (organs) of the body."
Blaha noted that BMI is not a strong measure of metabolic and cardiovascular risk, nor of abdominal or visceral fat. "Waist circumference and waist-to-hip ratio are good measures of abdominal/visceral fat. When added to BMI, they provide a much better assessment of body composition," he said.
Key Findings
The researchers analyzed people with either waist circumference or waist-to-hip ratio measurements, all of whom also had one of several heart disease outcomes, including fatal or non-fatal heart attack, fatal or non-fatal stroke (搜索), heart failure (搜索), atrial fibrillation (搜索) (AFib), total coronary heart disease (搜索), total cardiovascular disease (搜索), death from coronary heart disease, and death from cardiovascular disease and/or death from any cause.
The study found that people who were at a healthy weight or who had overweight, and had a clinically defined high waist circumference or waist-to-hip ratio, had a 15% to 50% higher risk for one of the listed heart disease problems.
"It is important to know that your weight or your BMI is not the end [of] the story," Blaha said. "Even if you do not have obesity by BMI (i.e., >30 mg/kg2), you may still have considerable abdominal/visceral fat that places you at higher metabolic and cardiovascular risk."
"The composition of your body matters, not just the weight," he added. "Our general goal will be to optimize lean body mass while reducing the amount of unhealthy abdominal or visceral fat."
The Mechanism Behind Visceral Fat
Cheng-Han Chen, MD, a board certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, who was not involved in this study, explained how excess belly fat may increase heart disease risk.
"Visceral fat that wraps around the internal organs in the abdomen is particularly known for being metabolically active, releasing chemicals that contribute to inflammation in the bloodstream," Chen explained. "These chemicals interfere with blood sugar regulation, blood pressure control, and cholesterol levels. These effects then increase the risk of developing cardiovascular disease (搜索)."
Palinski-Wade echoed this view, stating that "where you carry fat matters more than how much you carry, because visceral fat, the fat wrapped around abdominal organs, is metabolically active tissue that drives inflammation, insulin resistance, and artery damage in a way that fat under the skin elsewhere on the body doesn't."
Shifting Away From BMI Alone
Blaha noted that experts are beginning to move away from using BMI as the sole measure of weight and body composition, with growing recognition that visceral fat can increase health risks even in people whose BMI does not meet the threshold for obesity.
"Patients with normal weight or overweight can still have high metabolic and cardiovascular risk," he continued. "New obesity definitions are appreciating this, and are moving toward defining obesity using a combination of BMI and/or multiple measures of abdominal fat like waist circumference and waist-to-hip ratio."
Mir Ali, MD, bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, who was not involved in this study, cautioned that measuring waist circumference or waist-to-hip ratio carries variability. "When people measure, not everybody measures it at the same point," Ali explained. "So sometimes the people who measure it a little higher or lower get an inaccurate number."
He recommended that patients speak with their primary doctor to learn the correct way to measure waist circumference and to determine whether it is abnormal and what can be done about it.
Study Limitations
The researchers noted several limitations of the study, including that they did not have information on participants' physical activity, diets, or genetic risk for obesity, all of which can play a role in cardiovascular disease (搜索). Additionally, the study measured waist circumference and waist-to-hip ratio only once, limiting researchers' ability to determine how changes in abdominal fat over time may affect heart disease risk.
When it comes to reducing belly fat, Ali said there is no way to direct weight loss specifically to abdominal fat. "With weight loss in general, people will lose it all over, including abdominal fat," he said. He noted a common misconception that doing sit-ups will help lose abdominal fat, but that only develops the abdominal muscles. "So any kind of a good diet where you're reducing carbohydrates and sugars, and directing your body toward burning fat, that's going to help reduce abdominal fat as well," Ali said.