(You may want to read the first part before)
The Good, the Bad, and the Ugly Cholesterol
Still, insulin resistance is more than just a precursor to diabetes, even though the American Diabetes Association (ADA) now calls it exactly that—"prediabetes." All of that free-roaming insulin will sabotage your body's system for using and storing fats. Specifically, excess insulin jacks up triglyceride levels in the blood and lowers the level of HDL cholesterol by encouraging the liver to overproduce dangerous substances called very low-density lipoproteins (VLDL). (Quick refresher course: HDL is good cholesterol, LDL is bad cholesterol, and VLDL is Osama bin Laden—bad cholesterol.) The combination of high triglycerides and low HDL levels is a major risk factor for heart attacks, since it signals that the coronary arteries are likely being layered with plaque.
The deadly duo of high triglycerides and low HDL is also a key indicator of a recently discovered metabolic disorder known as syndrome X, which goes by the alias "insulin resistance syndrome." Other markers of syndrome X include inflammation of the blood-vessel walls and high blood pressure. Researchers aren't entirely certain whether insulin resistance causes syndrome X, or whether it's guilty by association. This much is known: If you have syndrome X—and as many as 25 percent of people do—your risk of a fatal heart attack doubles.
The Path of Least Resistance
If insulin resistance were a contagious disease, there would be no end to the hand-wringing news accounts about "the deadly scourge sweeping our nation. Details at 11." An astounding 41 million Americans have insulin resistance, according to a newly revised estimate by the ADA. Think about it: One out of every three people in your office, stuck in traffic around you, or cruising the aisles at the Hefty Mart has put himself on a collision course with diabetes and heart attack. "We're not on the cusp of a public-health emergency. We're in it," says M. James Lenhard, M.D., an endocrinologist and the director of the weight-management program at Christiana Care Health System in Wilmington, Delaware. Insulin resistance strikes especially hard in the 40-to-74 age group, where the rate hits 40 percent, although the real boom market of late is among men and women in their 30s.
How did insulin resistance snatch so many bodies while we were busy minding J.Lo's love life? Some men run a higher risk of the condition simply because they didn't choose their parents carefully enough. Diabetes in the family tree raises the odds; so does being African-American, Native American, Latino, or Asian-American, or a Pacific Islander. By one estimate, half of the risk of insulin resistance is hereditary. "Genes may put the bullet in the gun, but it's the environment that pulls the trigger," says Dr. Lenhard. And chances are, the finger on the trigger is a pudgy one.
The connection between fat and insulin resistance is powerful and consistent. Among obese individuals, 85 percent have some degree of insulin resistance. Conversely, even minor weight loss leads to an immediate improvement in insulin function. But exactly how flab fosters the decline in insulin sensitivity is unclear. The scariest theory: Our lard is somehow alive. "Fat is not an inert storage depot. It produces resistin, which has a negative effect on muscle tissue's ability to respond to insulin. The more overweight a person is, the more resistin will be produced," says Erik J. Henriksen, Ph.D., a professor of physiology at the University of Arizona college of medicine. "Fat also releases adiponectin, which has a positive effect on insulin response. But as individuals become more obese, they produce less." In effect, fat begets more fat in a negative-feedback loop.
Inactivity, and not just its fat by-product, may also play a crucial role in causing insulin resistance. We already know that insulin serves as a sort of ticket scalper that gains glucose entrance to a cell. But once inside the gate, hapless glucose can't find its seat without the help of chemical ushers called IRS-1 and GLUT-4. And this is where inactive men get into trouble. "Physical inactivity lowers the levels of IRS-1 and GLUT-4 and decreases their effectiveness," says Henriksen. Lack of exercise may also increase free fatty acids in the blood and step up the storage of visceral fat, both of which are leading suspects in the mystery of what causes insulin resistance, according to Henriksen.
As complex as the origins of insulin resistance are, stopping it in its tracks is surprisingly straightforward: Exercise, lose weight, and eat smart. Even modest effort in these areas yields big health dividends. Take what the Diabetes Prevention Program found when it carried out a major clinical trial involving more than 3,000 insulin-resistant people. The researchers showed that a 7 percent weight loss (about 14 pounds for a 200-pound man), coupled with walking for half an hour 5 days a week, reduced the risk of diabetes by 58 percent. "The bright side of insulin resistance is that it's like an early warning signal," says Cathy Nonas, R.D., director of obesity and diabetes programs for North General Hospital in New York City. "Catch it quickly, make the necessary lifestyle changes, and you can avoid diabetes, cardiovascular disease, and stroke."
Pounding Out the Risk
Mike Nevin heeded the warning. It took him a few days to recover from the one-two punch of being labeled obese and insulin resistant. Then he directed the mental toughness that had earned him a starting position on a Division I college football team toward the challenge of drastically improving his health.
"There was no way I was going to end up with diabetes, having a needle stuck in me several times a day," he says. Nevin immediately committed himself to a workout routine that included lifting weights 6 days a week and running 3 to 8 miles three times a week. "The first day I ran, I made it about a block and a half without stopping," he says. "The next day, I could run two squares farther on the concrete sidewalk. That's how I measured my progress."
While making his cells ravenous for energy through exercise, Nevin also overhauled his diet. He quit the gut-busting lunchtime routine of burgers and fries, stopped drinking beer, and swore off baked potatoes and white bread. Instead, he began eating a lot more vegetables and fruit, low-fat cheeses, and whole grains. He also substituted fish for some red meat. "This was the first time in my life that I combined diet and exercise.
I lost nearly 20 pounds a month in the first 4 months," says Nevin. "When I saw my doctor, he couldn't believe the change." The improvements could be seen in Nevin's blood profile, too: His triglycerides plummeted below 100, his LDL dropped, his HDL rose, and his blood sugar sank to 85. He eventually carved his weight down to 225 pounds, with a lean 17 percent body fat.
Not surprisingly, once he whipped himself back into shape, Nevin also rediscovered his need to compete. This past year, he ran his first half-marathon and earned a black belt in tae kwon do. "I'm proud of what I've done," he says, "but I'll tell you, the easiest way to lose 120 pounds is never to gain it."
Photo: The Age