The list of health risks tied to being overweight or obese seems to increase every year -- along with the nation's collective waistline. While losing weight can be challenging, there are new, compelling reasons to try to shed those extra pounds -- especially if they're around your middle.
Scientists used to think that fat was a relatively passive substance: It was simply stored energy. But recent research suggests that fat cells are biologically active. They secrete dozens of hormones and other chemicals that affect nearly every organ system in the body. When your weight is normal, these hormones and chemicals keep you healthy: They dampen your appetite after a meal, burn stored fat, regulate insulin and protect against diabetes -- among other functions.
But if you are overweight, you have many more fat cells than a normal-weight person -- and the cells are bigger. These super-sized fat cells release more hormones and chemicals than your body needs, especially if they constitute belly fat (also known as visceral fat). This flood of chemicals can take a toll on your health, increasing your risk of heart disease, diabetes, stroke and even cancer.
Belly Fat and Disease
Scientists are still learning how substances secreted by abdominal fat cells harm the body. Recent research shows that these cells produce proteins that can damage the body in different ways. One type of protein, a known precursor to angiotensin, constricts blood vessels, causing blood pressure to rise. Another protein called retinol-binding protein 4 (RBP4) increases insulin resistance, which can lead to clogged arteries and heart attack. Still other proteins can trigger low-level inflammation, which has been tied to heart disease, diabetes and other chronic diseases such as cancer.
Visceral fat has been linked to cancer in other ways, too. After menopause, the ovaries stop producing estrogen and fat tissue becomes the main source of this hormone. A woman who is obese has many extra fat cells that are busy churning out estrogen. All those extra hormones can fuel the growth of breast tumors. Both men and women with excessive belly fat also have an increased risk of colorectal cancer.
Even the brain can be impacted by excessive abdominal fat. A 2005 study of older people linked larger bellies with declines in memory and language. Extra belly fat also carries an increased risk for dementia and asthma.
Direct Line to the Liver
What makes belly fat so much more dangerous than subcutaneous fat (the kind you can pinch with your fingers that's on your hips and lower body)? Scientists think that visceral fat produces greater amounts of harmful chemicals than subcutaneous fat. Visceral fat's location makes it more dangerous, too.
Visceral fat is deep in the abdomen where it surrounds critical organs, including the liver. Blood that circulates through visceral fat drains directly into the liver via the portal vein. Dangerous substances produced by visceral fat pour straight into the liver. One of these substances -- free fatty acids -- disrupts the liver's production of fats and offsets the balance of LDL and HDL cholesterol. These fatty acids also increase the risk of fatty liver disease and hepatitis B.
How can you tell if you have too much visceral fat? If you have a lot of subcutaneous fat on your belly, the kind you can pinch, chances are good there is lots of visceral fat underneath. Belly fat increases with age, especially among women. Even if a woman's weight doesn't change as she reaches middle age, her proportion of body fat usually increases, and much of it ends up around the abdomen.
For both women and men, a tape measure is the best tool for assessing how much visceral fat you have. Measure your waist just above your hipbone without sucking in your stomach. If you're an average-sized woman, a waist measurement of 35 inches or more is considered too much belly fat. For most men, a waist circumference greater than 40 inches is cause for concern.
The good news is that belly fat responds especially well to dieting and to aerobic exercise. That's because visceral fat metabolizes into fatty acids more easily than subcutaneous fat. There's more good news: Once you start to lose belly fat, many of the harmful effects of those extra fat cells can be reversed -- including high blood pressure and high cholesterol.
Eat less, But Eat Well
To lose weight, you do need to reduce the amount of calories you take in, but don't make too dramatic a reduction. It will slow down your metabolism and make it harder to lose weight. Instead, decrease portion sizes and make healthy food choices: Eat lots fresh vegetables and fruits along with lean protein.
Check food labels and avoid trans fats and saturated fats, choosing polyunsaturated fats instead. Eat whole grains as much as possible and avoid refined-grain pasta and white bread. Also limit your intake of processed foods and sugary drinks. Women should be sure to intake plenty of calcium. One study showed that the more calcium women consumed, the less visceral fat they gained.
Make Exercise a Habit Exercise is also critical if you want to shed belly fat. Do some form of aerobic exercise -- fast walking, jogging, biking or an aerobic exercise class -- for at least 30 minutes a day. You don't have to do an intense workout if you reduce your calorie intake, too. A 2009 study found that belly fat responded just as well to moderate exercise as intense exercise if calorie consumption was reduced. Find ways to work exercise into your daily life, too. Take stairs instead of taking an elevator or park a few blocks from your destination and walk. Exercising with weights can also help take off belly fat by adding muscle, which increases your metabolism.
Some More Advice
If you smoke, quit. In addition to all the other health risks, smoking causes you to store more fat in your belly. And try to reduce the amount of stress in your life. The stress hormone cortisol is associated with visceral fat increase -- even in women who are not overweight.
Learn more about visceral fat and fat distribution:TheVisualMD.com: Measuring Fat