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One of my most in-shape friends recently began worrying about “pooling fat.” It turns out this fat, also called “belly fat” and “central obesity,” can be a cause for concern. Normal-weight adults with a normal body mass index (BMI) — the ratio of a person’s weight to their height — but an abnormally large waist might be at higher risk of death from cardiovascular disease than those with a high BMI.
“Waist size matters, particularly in people who are a normal weight,” Francisco Lopez-Jimenez, of the Mayo Clinic and senior author on a study analyzing data on more than 15,000 adults over a period of 14 years, told the Washington Post. The study focused on people’s waist-to-hip ratio: a waist measuring larger than the hips reflects excess fat storage around the middle. Central obesity is also defined clinically as a waistline of more than 35 inches in women and more than 40 inches in men, according to the Centers for Disease Control and Prevention.
During the study period, men with “normal-weight central obesity” had twice the mortality risk of men rated overweight or obese by BMI, and had 78% higher risk of death from cardiovascular disease than men with a similar BMI but no central fat. For normal-weight women with belly fat, the risk of death was 32% more than that for obese women without excess pounds around the middle; and central obesity more than doubled their risk of death from heart disease. “We need to talk about waist loss and not weight loss,” Paul Poirier of the Quebec Heart and Lung Institute commented on the study in an email to the Post.
Fifty-four percent of U.S. adults now have central obesity — compared to 46% in 1999-2000 — a body type known as apple-shaped, because the abdomen protrudes in a “pot” or “beer” belly; the alternative kind of fat creates a pear shape, with fat accumulating around the hips and butt. Belly fat consists of deep or visceral fat pooling around the abdominal organs, in contrast to the fat beneath the skin, and can promote inflammation throughout the body, increasing the risk for heart disease, diabetes, stroke and colon cancer.
Although the cause of belly fat is not clear, there is some evidence that low-carbohydrate diets help combat it. On the other hand, a study of people age 65 and older who drank two or more diet sodas a day had waist-size increases six times greater than non-drinkers — about 3.2 inches compared with .8 inches — while people who drank an occasional diet soda gained about 1.8 inches. Belly fat-gain was most pronounced in people who were already overweight.
Artificial sweeteners may behave just like sugar in the body, provoking spikes in insulin levels and shifting the body from burning fat to storing it. Or they may alter gut bacteria, making the body more vulnerable to insulin resistance and glucose intolerance, which can lead to weight gain. Snacking also appears to contribute to abdominal fat — maybe because mid-morning snackers tend to eat more throughout the day than others.
Avoiding snacks is one of “10 daily habits that blast belly fat” as described in the “Zero Belly Diet,” by David Zinczenko. The book also recommends dark chocolate to help shrink abdominal fat, because of the flavonoids, which can fight inflammation. The chocolate must be at least 70% cacao, and not “alkalized.”
As for exercise to pare down belly fat, aerobic exercise seems to work better than interval training. In one study comparing the two kinds of exercise, done three days a week over a 12-week period, those who performed interval training on an exercise bike for 24 minutes each time actually gained .7 percent abdominal fat, while those on the same diet doing 45 minutes of continuous moderate cycling lost nearly 3 percent.
Sedentary women who began moderate exercise twice a week lost about 2% of their total body fat but 10% of the visceral fat, according to a study at the University of Alabama at Birmingham. According to one review, programs combining aerobic exercise with occasional weight training worked better to reduce belly fat than either type of exercise alone. But University of Alabama’s Dr. Gary Hunter warns against one exercise that will not affect the waistline: the situp. “You’re better off going for a walk,” says Hunter.
—Mary Carpenter