Until 1993 all fat was considered equally unhealthy, but a study at that time found that persons with increased visceral fat (apple shape) had a higher risk of heart disease than those with fat around the thighs and bottom (pear shape). Later studies have linked excess abdominal fat to an increased risk of heart disease, diabetes, insulin resistance, breast cancer, high cholesterol, hypertension and other health problems.
Abdominal fat refers not to flab that you can see just under the skin–whether it shows up in love handles near the waist or in dimpled areas on the thighs or bottom–but fat that’s located inside the body cavity, wrapping itself around inner organs. Visceral fat can crowd organs and blood vessels. It also lies close to the portal vein, which carries blood from the intestines to the liver. As a result, substances released by fat cells, such as free fatty acids, have a pathway to the liver where they can influence production of cholesterol.
Fat cells are far more active biologically than was once believed, and visceral fat in particular produces hormones that influence appetite and the body’s response to insulin. They may also pump out chemicals that promote low-level inflammation and insulin resistance.
The pear shape is generally more common among young women than men. It is usually attributed to hormones and heredity. After menopause, however, women tend to be equally vulnerable to abdominal fat, a change that’s caused in part by the sharp drop in estrogen that occurs at that time. The drop in estrogen is also associated with increased production of cortisol, a stress hormone that promotes the accumulation of abdominal fat.
Unhealthy Lifestyle Patterns
During the last 15 years scientists began looking at the unique characteristics of visceral fat, and much remains to be learned. It appears that it’s a result of unhealthy patterns of both diet and physical activity. One study found that visceral fat increased with the amount of fat in a person’s diet–particularly saturated fats such as meat and butter. According to this study, persons most likely to have measurable visceral fat were those getting more than 30 percent of their calories from fat.
Physical inactivity also plays a role. According to one study, subjects with the lowest level of cardiovascular fitness had twice as much abdominal fat as those with the highest level of fitness, even among subjects with the same body mass index (BMI). Waist circumference is now believed to be a better measure of health and fitness than either weight or BMI.
When fat is removed from the body through liposuction, visceral fat remains untouched. And so apparently do the health problems. In a study of 15 obese women undergoing liposuction [New England Journal of Medicine, 2004] removal of as much as 23 pounds of subcutaneous fat had no short-term effect on the patient’s blood pressure, blood sugar, cholesterol or response to insulin.
Abdominal fat apparently responds better to weight loss programs that include at least some degree of exercise. A study of 33 obese postmenopausal women with type 2 diabetes found that subjects who lost weight through a very low-calorie diet over 14 weeks had no loss of visceral fat. On the other hand, those participating in either supervised aerobic exercise or a combination of dieting and exercise lost visceral fat as well as weight.
A study at Duke University found that subjects who remained sedentary had a nine percent gain in visceral fat over six months while those who walked or jogged 12 miles a week gained none. Subjects who walked or jogged 20 miles a week lost both visceral and subcutaneous fat.
Size of Fat Cells Matters
An obese person has two to three times more fat cells than a person of normal weight. In addition, fat cells are long-lived and capable of growing almost indefinitely. The size of abdominal fat cells apparently matters, at least in terms of diabetes risk. In a study at Wake Forest University, weight loss subjects were placed into three groups–one using diet alone, one using diet plus leisurely walking and a third, diet plus brisk walking. While all three groups lost weight, fat mass and inches around the waist and hips, only the two exercise groups showed a decrease in the size of their abdominal fat cells.
Exercise reduces fat not only because it burns calories but also because it builds muscle. Compared to fat cells, muscle cells burn more calories. And a favorable muscle to fat ratio makes cells more sensitive to the action of insulin. Strength training is considered an important part of a balanced exercise program, and it’s an effective way to fight abdominal fat. A two-year study of overweight and obese women aged 24 to 44 found that those doing strength training with weights twice a week reduced their total body fat by about four percent and were more successful than other subjects in keeping off visceral fat.
The only exercise that’s a waste of time, unfortunately, is what many Americans look to first when they want to get rid of a protruding tummy–hundreds of situps a day or workouts on those “easy-to-use” ab machines advertised on TV. Regardless of how much you strengthen your abdomen muscles, they are not going to look flat unless you get rid of the visceral fat underneath them; and they’re not going to show up if there’s subcutaneous fat on top.
The way to get rid of a beer belly is to build muscle throughout your body through a variety of exercises–three to five days a week of aerobic activity such as running, brisk walking or biking; strength training with weights and stretching to keep muscles limber. In moderation, the beer won’t give you a belly but sitting on the couch too long will!
Michelle Herbert Thomas, PharmD, CDE
Clinical Director
Richmond Apothecaries, Inc.
