TRENTON, N.J. — Getting fatter around the middle? Have a family history of heart disease or diabetes? You could be headed for the same trouble, especially if you're over 40 and female.

There are no obvious symptoms from high blood sugar or the condition called insulin resistance, so few people realize it is creeping up and putting them on the path to diabetes, heart disease or both.

But insulin resistance, a type of pre-diabetes, is a growing national problem: Some experts believe half of all overweight or obese American adults are insulin-resistant.

Yet, even many women with a family history of heart disease or diabetes don't know they need to eat a healthier diet and get more exercise to avoid those problems — two of the nation's top killers.

"We think this is a very important new issue for women," said Audrey Sheppard, chief executive of the National Women's Health Resource Center. "There's very little awareness."

As women enter the years leading to menopause, the hormonal changes that trigger hot flashes and end menstruation make women more likely to add fat around the waistline than in other places. A key tipoff of looming trouble is a waistline over 34 inches, according to one expert. (For men, it's 40 inches.)

Fat also builds up in the liver and other vital organs, predisposing them to insulin resistance, a condition in which insulin no longer can inject enough glucose into the body's cells for fuel, said Dr. David Katz, co-founder of the Yale Prevention Research Center and author of several books on weight control.

The body's compensatory mechanisms eventually fail, blood pressure rises along with levels of blood sugar and blood fat — making cells even more resistant to insulin. Diabetes, heart disease or both often follow.

"That's the sequence that's occurring in tens of millions of American adults" and an increasing number of children amid the country's obesity epidemic, said Katz. "It's an enormous problem. We're just starting to get doctors' attention."

Besides a family history of heart disease or diabetes, women who had diabetes during pregnancy or who had a baby 9 pounds or heavier are at higher risk of insulin resistance.

Frequent fatigue and cravings for sweets, bread and pasta also may be linked to the problem. But Dr. Henry Kahn, a chronic disease epidemiologist with the U.S. Centers for Disease Control and Prevention, said those are vague symptoms that could have other causes.

The women's resource center, based in Red Bank, N.J., has just begun a new public health campaign targeting women aged 40 to 65 because they are at greater risk than others and often hold of the role of Dr. Mom, serving as monitor for the whole family's health.

Besides explaining on its Web site how uncontrolled blood sugar harms the body, the center offers tips for a healthy blood sugar level and suggests questions patients can ask a doctor.

Among research showing the benefits of a healthy lifestyle is a recent CDC study that found modestly overweight adults who worked with nutrition and exercise experts reduced their risk of diabetes by nearly 60 percent over several years, compared with a group that made no changes, said Kahn.

Lalita Kaul, an American Dietetic Association spokeswoman and professor of nutrition at Howard University Medical School, said over the last 25 years, about 70 percent of her patients at risk of diabetes have been able to control their blood sugar with diet and lifestyle changes.

The key diet changes, she said, include eating at least five servings of fruits and vegetables daily; cutting down on sugar and desserts while eating more whole grains; eating less saturated fat and using healthier cooking oils; eating salmon and other fish rich in essential fatty acids a few times a week; and avoiding prepared foods high in sodium, which pushes up blood pressure.