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Abdominal Obesity and Your Health
Last reviewed on January 10, 2013
By Harvey B. Simon, M.D.
Harvard Medical School
"How much should I weigh, doc?" It's a common question and an important one. It's common because about two-thirds of all Americans weigh more than they should. It's important because excess weight goes far beyond an unflattering figure. Obesity:
- Is responsible for high levels of LDL ("bad") cholesterol and triglycerides.
- Lowers HDL ("good") cholesterol at the same time.
- Impairs the body's responsiveness to insulin, raising blood sugar and insulin levels.
- Contributes to major causes of death and disability, including heart attacks, strokes, high blood pressure, cancer, diabetes, osteoarthritis, fatty liver, and depression.
- Is responsible for about 1,000 deaths in the U.S. each day.
Given these risks, it's no wonder that you want to know how much you should weigh. But this common and important question is actually the wrong question. For health, the issue is not how much you weigh, but how much abdominal fat you have.
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In the past few years, a number of studies have called attention to the importance of abdominal obesity. Some of the research shows that abdominal obesity is a better predictor of risk than body mass index (BMI).
Shortcomings of the BMI
Although the BMI is the official standard, it has several flaws.
- Highly trained athletes with big muscles and little body fat can have BMIs up to 32.
- The BMI may fail to accurately reflect body fatness in adults who have lost substantial amounts of muscle.
- The most important problem is that the BMI reflects total body fat without regard to how the fat is distributed. And although no excess fat is good, excess abdominal fat is the worst offender.
For example, a 2008 study of 245,533 Americans found that a large waist circumference was linked to an increased death rate, even in people with normal BMIs. Another study of 2,229 heart attack victims reported that patients with a large waist circumference had an increased rate of death, even if they had a low BMI.
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The Inside Story
What makes abdominal fat so harmful? Scientists don't know for sure, but new research is providing strong clues.
Abdominal fat comes in two different forms. The first form is subcutaneous fat. It is located just beneath the skin. This fat behaves like the fat elsewhere in the body. It's no friend to your health, but it's no special threat either. The second kind is visceral fat. It's found around the internal organs and is the true villain. Why?
One of the earliest explanations was that visceral obesity was linked to overactivity of the body's stress response, producing jolts of stress hormones such as adrenaline and cortisol.
A newer explanation is that visceral fat cells release their metabolic products directly into the blood that goes right to the liver. As a result, visceral fat cells that are enlarged and stuffed with excess triglycerides pour free fatty acids into the liver. (All fats come in the form of free fatty acids.) This can be toxic to the liver. Free fatty acids also accumulate in the pancreas, heart and other organs where they do damage.
A third theory shows the complex nature of fat cells. Scientists once believed that fat cells were just a place for excess calories to be stored as fat. But it's now clear that in addition to hoarding excess energy, fat cells produce a large number of proteins that enter the bloodstream and affect other organs. Some of these proteins are damaging, others are protective. Visceral fat cells produce lots of the harmful substances, but few of the helpful ones.
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Measuring Abdominal Obesity
The most accurate way measure visceral fat is with computed tomography (CT scanning) or magnetic resonance imaging (MRI). A much easier way, however, is to determine the waist-to-hip ratio. But many experts are now turning to an even simpler technique: waist circumference.
To measure your waist circumference properly you will need a cloth measuring tape that can't be stretched, not the stiff metal tape from your toolbox:
- Take your shoes off and stand with your feet together.
- Be sure your belly is bare. Relax and exhale. Don't suck your belly in; it may give you a better number, but it won't improve your health. And using your belt size instead is unreliable.
- Measure your waist at the navel. Be sure to keep the tape parallel to the ground. Record the measurement to the nearest one-tenth of an inch, and then repeat the measurement to be sure you've got it right.
- Check the table below to see what your waist size means for your health.
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37 inches and under
31.5 inches and under
40 inches and over
35 inches and over
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So what can you do to reduce your waist size? Forget abdominal crunches and sit-ups. They are good for increasing muscle tone, which may improve your profile, but they won't selectively burn up abdominal fat. Gadgets that promise spot fat reduction are even worse; they'll have you wasting time and money without reducing your waist.
Forget liposuction and apronectomy ("mini tummy tuck"). Surgery can remove subcutaneous fat from your midsection but not visceral fat. Cosmetic surgery will improve your appearance and reduce your waist circumference, but it won't do a thing for your metabolism or health.
Remember the basics. The only way to reduce visceral fat is to lose weight by burning more calories with exercise than you take in from food. Sustained weight loss requires both calorie restriction and increased exercise. Here are some tips:
- Reduce your portion sizes.
- Choose your foods wisely. Avoid foods that are high in sugar and/or fat. They are calorie-dense, and they slide down all too easily. Instead, favor fruits, vegetables, and whole-grain products. They are high in fiber, take longer to eat, and may be more filling. A medium-size chocolate chip cookie and a medium-size apple each have about 100 calories (if they are really medium size!). Now consider eating five cookies or five apples. It's obvious that most people can easily knock off the cookies, but few can finish the apples.
- Exercise more. Walking two miles a day will substantially reduce your risk of heart disease, stroke, diabetes, hypertension and premature death. It will also burn calories. A 200-pound man will use about 220 calories in 30 to 40 minutes of brisk walking. This alone means a nearly 30-pound weight loss in a year without any dietary changes. Exercise also helps keep weight off, unlike the heavily hyped fad diets. Second, it will burn off extra abdominal fat, something abdominal crunches and "spot reducing" schemes never do.
- For faster weight loss, eat less or exercise more.
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The Shape of Man
Abdominal obesity goes by many other names, including upper body obesity, truncal obesity, central obesity and visceral obesity. In more colorful terms, it's also known as the beer belly, the apple shape, and the spare tire. Since this type of fat distribution is more common in males than females, perhaps it should be known as the shape of man.
By any name, abdominal obesity is the shape of risk and abdominal obesity is increasing even faster than BMI in our corpulent society. But with a simple program of diet and exercise, men with an apple shape can pare down. And if you change your "spare tire," you'll spare your health.
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Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.