Should you worry about your waistline?

Extra padding around your midsection goes by many different names — a spare tire, muffin top, or love handles. Too much of any type of fat isn't healthy, but some forms are worse than others. The flab you can pinch between your fingers is known as subcutaneous fat, which lies just beneath the skin. A more worrisome type of fat lies deep within the abdominal cavity, padding the space between your organs (see illustration).

Known as visceral fat, it does more than add inches around your waistline; it also raises your risk of cardiovascular problems. "Growing evidence suggests that your waist circumference is a better predictor of heart disease than your body mass index," says Dr. Osama Hamdy, medical director of the Obesity Clinical Program at Harvard-affiliated Joslin Diabetes Center. Body mass index (BMI), an indirect estimate of body fat based on height and weight, doesn't distinguish between the different types of fat. "People can have what's considered a healthy BMI but still have a large belly and visceral fat," says Dr. Hamdy.

Another measurement, the waist-to-hip ratio, correlates with visceral fat. But there's no need to do that extra hip measurement or math because waist circumference alone is strongly linked to visceral fat, says Dr. Hamdy. Just make sure you measure correctly (see "Gut check: How to measure your midsection").

Why is visceral fat dangerous?

Visceral fat is also a marker for ectopic fat, which refers to fat that accumulates inside organs (such as the liver, heart, and pancreas) and muscles. Both type of fat are closely tied to metabolic problems, especially type 2 diabetes — which, in turn, is a potent risk factor for heart disease. In addition, visceral fat secretes hormones and other inflammatory factors, collectively called adipokines or cytokines, which trigger a buildup of fatty plaque inside arteries (atherosclerosis).

Who's at risk?

Your genes, ethnic background, and sex all influence how likely you are to accumulate visceral fat. Native Americans (notably the Pima tribe), Hispanics, and people living in India and South Asia have a higher likelihood of abdominal obesity (as well as diabetes). In addition, white men and black women tend to accumulate relatively more visceral fat compared with black men and white women.

What helps to banish a big belly?

Although some people are predisposed to larger midsections, there's a lot you can do to remedy the problem, says Dr. Hamdy.

Get regular exercise. Sit-ups or other abdominal exercises won't shrink your belly. Instead, you need to burn calories to lose fat and build muscle through a combination of aerobic and strength training. Aim for at least 30 minutes daily of moderate-intensity exercise (like brisk walking), and do strength-based exercise at least two days per week.

Follow a healthy, reduced-carbohydrate diet. Avoid foods and drinks with added sugars and other simple carbohydrates that spike blood sugar and encourage your body to store fat. These include foods made with white flour (common culprits include what Dr. Hamdy calls the "P's and B's": pasta, pizza, pretzels, bread, and bagels) and starchy foods, such as white potatoes, white rice, and corn.

Try time-restricted eating. Some research suggests this strategy may lower blood sugar levels and reduce visceral fat. There are many ways to structure your eating; for example, you might eat only between 9 a.m. and 5 p.m., and fast during the other 16 hours. This not only limits calorie intake but also kick-starts the body's fat-burning process.

Illustration by Scott Leighton