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Visceral fat more of a health concern than subcutaneous fat

Though the term might sound dated, "middle-age spread" is a greater concern than ever. As people go through their middle years, their proportion of fat to body weight tends to increase — more so in women than men. Extra pounds tend to park themselves around the midsection.

At one time, we might have accepted these changes as an inevitable fact of aging. But we've now been put on notice that as our waistlines grow, so do our health risks. Abdominal, or visceral, fat is of particular concern because it's a key player in a variety of health problems — much more so than subcutaneous fat, the kind you can grasp with your hand. Visceral fat, on the other hand, lies out of reach, deep within the abdominal cavity, where it pads the spaces between our abdominal organs.

Visceral fat has been linked to metabolic disturbances and increased risk for cardiovascular disease and type 2 diabetes. In women, it is also associated with breast cancer and the need for gallbladder surgery.

Are you pear-shaped or apple-shaped?

Fat accumulated in the lower body (the pear shape) is subcutaneous, while fat in the abdominal area (the apple shape) is largely visceral. Where fat ends up is influenced by several factors, including heredity and hormones. As the evidence against abdominal fat mounts, researchers and clinicians are trying to measure it, correlate it with health risks, and monitor changes that occur with age and overall weight gain or loss.

The good news is that visceral fat yields fairly easily to exercise and diet, with benefits ranging from lower blood pressure to more favorable cholesterol levels. Subcutaneous fat located at the waist — the pinchable stuff — can be frustratingly difficult to budge, but in normal-weight people, it's generally not considered as much of a health threat as visceral fat is.

Research suggests that fat cells — particularly abdominal fat cells — are biologically active. It's appropriate to think of fat as an endocrine organ or gland, producing hormones and other substances that can profoundly affect our health. Although scientists are still deciphering the roles of individual hormones, it's becoming clear that excess body fat, especially abdominal fat, disrupts the normal balance and functioning of these hormones.

Scientists are also learning that visceral fat pumps out immune system chemicals called cytokines — for example, tumor necrosis factor and interleukin-6 — that can increase the risk of cardiovascular disease. These and other biochemicals are thought to have deleterious effects on cells' sensitivity to insulin, blood pressure, and blood clotting.

One reason excess visceral fat is so harmful could be its location near the portal vein, which carries blood from the intestinal area to the liver. Substances released by visceral fat, including free fatty acids, enter the portal vein and travel to the liver, where they can influence the production of blood lipids. Visceral fat is directly linked with higher total cholesterol and LDL (bad) cholesterol, lower HDL (good) cholesterol, and insulin resistance.

Insulin resistance means that your body's muscle and liver cells don't respond adequately to normal levels of insulin, the pancreatic hormone that carries glucose into the body's cells. Glucose levels in the blood rise, heightening the risk for diabetes. Now for the good news.

Exercise and dieting can help you get rid of belly fat

So what can we do about tubby tummies? A lot, it turns out. The starting point for bringing weight under control, in general, and combating abdominal fat, in particular, is regular moderate-intensity physical activity — at least 30 minutes per day (and perhaps up to 60 minutes per day) to control weight. Strength training (exercising with weights) may also help fight abdominal fat. Spot exercising, such as doing sit-ups, can tighten abdominal muscles, but it won't get at visceral fat.

Diet is also important. Pay attention to portion size, and emphasize complex carbohydrates (fruits, vegetables, and whole grains) and lean protein over simple carbohydrates such as white bread, refined-grain pasta, and sugary drinks. Replacing saturated fats and trans fats with polyunsaturated fats can also help.

Scientists hope to develop drug treatments that target abdominal fat. For now, experts stress that lifestyle, especially exercise, is the very best way to fight visceral fat.