Judging by the exploding popularity of athleisure clothes, many of us have decided to deal with the extra pandemic pounds around the midsection with the miracle of elastic. Unfortunately, those extra inches taxing your waistband may also be hurting your heart. A new study by Oxford University researchers has found that every extra inch of belly fat increases the relative risk of heart failure by 11 percent, making waist circumference a greater threat to heart health than overall weight. The research was presented at the 2022 European Society of Cardiology Congress, held August 26–29 in Barcelona, Spain.
The fact that belly fat or weight around the middle was found to be associated with a greater risk of heart failure isn’t too surprising, but it’s a risk factor that more people should be aware of, says Francisco Lopez-Jimenez, MD, a cardiologist and researcher at Mayo Clinic in Rochester, Minnesota, who was not involved in this study. Obesity is a known risk factor for heart failure, but we need to drill down further, he says. “The type of fat can make a big difference in a person’s risk for cardiac events and heart failure,” says Dr. Lopez-Jimenez.
Why Belly Fat Matters When It Comes to Heart Health
Overweight and obesity in the United States has continued to creep up in the past few decades, and so has waist circumference. The average waist measurement for women is 38.7, up from 36.3 in 1999–2000, and men’s midsections are an average of 40.5 inches, up from 39 inches in 1999–2000, according to the Centers for Disease Control and Prevention (CDC).
Where we carry our fat affects our heart and overall health, says Lopez-Jimenez. “Deeper belly fat, which is the visceral fat that accumulates around abdominal organs such as the pancreas, liver, and the small and large intestines, is fundamentally different from the fat that’s under the skin,” he says. This type of fat has been more associated with inflammation, another factor that affects the heart, arteries, and other areas, says Lopez-Jimenez.
There isn’t a standard recommended waist size, but in general, smaller is thought to be better, as long as your BMI falls within the healthy range, he says. The definition of abdominal obesity for women is greater than 35 inches, and for men it’s greater than 40 inches. One good rule of thumb is to keep your waist size less than half your height, he says. That means someone 6 feet tall should ideally have a waist size less than 36 inches.
Waist circumference is not your pants size or measured where you button your pants — the measurement is taken around the middle at or near the belly button, according to the Centers for Disease Control and Prevention (CDC).
Risk of Heart Failure Increased With Every Extra Inch of Belly Fat
To examine the relationship between heart failure and BMI, waist circumference, and waist-hip ratio, researchers analyzed data from the UK Biobank on 428,087 people. The UK Biobank is an international health resource that collected blood, urine, and saliva samples along with detailed health information for research on a wide range of illnesses from more than half a million people throughout England, Wales, and Scotland between 2006 and 2010.
Participants were 56 percent women and 44 percent men and between the ages of 40 and 70, with an average age of 56 years old. The average waist circumference was 33 inches for women and 38 inches for men, and the average BMI was 26.9 for women and 27.7 for men.
A person with a BMI of 25 to 29.9 is considered overweight, and a person with a BMI of over 30 is considered to have obesity. BMI is calculated based on a person’s weight and height; the same formula is used for both men and women.
Researchers divided the participants into quintiles (five groups) in each area — BMI, waist circumference, and waist-to-hip ratio — from highest to lowest, so that people whose numbers were average (among the participants) would be placed in the middle quintile.
During the nearly 13-year follow-up there were 8,669 first-ever incident heart failure (HF) events: 5,205 in men and 3,464 in women. Each additional inch over a healthy waist size was associated with a higher risk of a cardiac event, such as heart attack, stroke, or irregular heart rhythm.
People in the group with the largest waistlines were 3.21 times more likely to suffer from cardiovascular health problems than those with the smallest waists. Those with the highest body mass index, or BMI, were only 2.65 times more likely to suffer heart failure than those with the lowest. Every extra unit of BMI increased the chances of heart failure by 9 percent.
Why Belly Fat Increases the Risk of Heart Failure
An estimated 6.2 million people in the United States have HF, and it contributes to 1 in 8 deaths, according to the Centers for Disease Control and Prevention (CDC).
When a person has HF, the heart can’t pump enough blood to meet the body’s requirements for oxygen and blood, according to the American Heart Association (AHA). The heart tries to compensate in different ways — it enlarges, develops more muscle mass, and it pumps faster. The rest of the body also tries to make up for the deficit by diverting blood away from less-important tissues and organs, and the blood vessels narrow to keep blood pressure up, according to the AHA.
There are several ways in which obesity contributes to heart failure, says Lopez-Jimenez. “Indirectly, central obesity is a major risk factor for high blood pressure, and high blood pressure is one of the main factors leading to heart failure,” he says.
More directly, obesity increases the release of some of the hormones in the blood system that make the heart become thicker, also called hypertrophy, he says. “The walls of the heart become thicker and eventually become stiffer, and this keeps the heart from being able to expand enough to get the amount of blood it needs to pump out to the other organs,” says Lopez-Jimenez.
Obesity makes the heart have to work harder, too, he says. “People with obesity will have more blood than people at a healthy weight. Every pound of fat requires more blood, and so someone with 40 or 50 pounds of extra fat is going to have a considerably higher amount of blood,” says Lopez-Jimenez. “That’s relevant for heart failure because it means the heart has to pump more at any given minute; eventually the heart gets tired and gives out,” he says.
People Who Are ‘Skinny Fat’ Have an Increased Risk of Death Due to Heart Attack or Stroke
One thing the study doesn’t really address is the part of the population that has a larger belly or waist circumference but is still a normal weight according to their BMI, known as normal weight obesity, says Lopez-Jimenez. “Evidence suggests that these people are at an even higher risk of death [overall] and death due to cardiac events,” he says.
If a person has a normal BMI but an increased waist circumference, they probably don’t have enough muscle mass, he explains. Muscle matters for a few reasons — it plays an important protective role and helps the heart, and it is crucial for metabolic health and burning energy, says Lopez-Jimenez.
“Unfortunately, many people with normal weight obesity don’t know they are at risk — they think they are healthy and don’t feel compelled to lose weight or exercise. We’re trying to increase awareness, because this is something that has been missed for decades, but it’s a risky combination for heart health,” he says.
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