If you do nothing else today to protect your health, consider taking an honest measurement of your waist. Stand up straight, exhale (no sucking in that gut!) and with a soft tape measure record your girth an inch or two above your hip bones.

The result has far greater implications than any concerns you might have about how you look or how your clothes fit. In general, if your waist measures 35 or more inches for women or 40 or more inches for men, chances are you’re harboring a potentially dangerous amount of abdominal fat.

Subcutaneous fat that lurks beneath the skin as “love handles” or padding on the thighs, buttocks or upper arms may be cosmetically challenging, but it is otherwise harmless. However, the deeper belly fat — the visceral fat that accumulates around abdominal organs — is metabolically active and has been strongly linked to a host of serious disease risks, including heart disease, cancer and dementia.

You don’t even have to be overweight or obese to face these hazards if you harbor excess fat inside your abdomen. Even people of normal weight can accumulate harmful amounts of hidden fat beneath the abdominal wall. Furthermore, this is not fat you can shed simply by toning up abdominal muscles with exercises like situps. Weight loss through a wholesome diet and exercise — activities like walking and strength-training — is the only surefire way to get rid of it.

Until midlife, men usually harbor a greater percentage of visceral fat than women do, but the pattern usually reverses as women pass through menopause. Few females seem to escape a midlife waistline expansion as body fat redistributes and visceral fat pushes out our bellies. Even though in my eighth decade I weigh less than I did at age 13, my waist is many inches bigger.

Here’s why visceral fat cells are so important to your well-being. Unlike the cells in subcutaneous fat, visceral fat is essentially an endocrine organ that secretes hormones and a host of other chemicals linked to diseases that commonly afflict older adults. One such substance is called retinol-binding protein 4 (RBP4) that was found in a 16-year study of nurses to increase the risk of developing coronary heart disease. This hazard most likely results from the harmful effects of this protein on insulin resistance, the precursor to Type 2 diabetes, and development of the metabolic syndrome, a complex of cardiac risk factors.

The Million Women Study conducted in Britain demonstrated a direct link between the development of coronary heart disease and an increase in waist circumference over a 20-year period. Even when other coronary risk factors were taken into account, the chances of developing heart disease were doubled among the women with the largest waists. Every additional two inches in the women’s waist size raised their risk by 10 percent.

Cancer risk is also raised by belly fat. The chances of getting colorectal cancer were nearly doubled among postmenopausal women who accumulate visceral fat, a Korean study found. Breast cancer risk increases as well. In a study of more than 3,000 premenopausal and postmenopausal women in Mumbai, India, those whose waists were nearly as big as their hips faced a three- to four-times greater risk of getting a breast cancer diagnosis than normal-weight women.

A Dutch study published last year linked both total body fat and abdominal fat to a raised risk of breast cancer. When the women in the study lost weight — about 12 pounds on average — changes in biomarkers for breast cancer, like estrogen, leptin and inflammatory proteins, indicated a reduction in breast cancer risk.

Given that two-thirds of American women are overweight or obese, weight loss may well be the single best weapon for lowering the high incidence of breast cancer in this country.

Perhaps most important with regard to the toll on individuals, families and the health care system is the link between abdominal obesity and risk of developing dementia decades later. A study of 6,583 members of Kaiser Permanente of Northern California who were followed for an average of 36 years found that those with the greatest amount of abdominal obesity in midlife were nearly three times more likely to develop dementia three decades later than those with the least abdominal fat.

Having a large abdomen raised dementia risk in the women even if they were of normal weight overall and lacked other health risks related to dementia like heart disease, stroke and diabetes.

Among other medical problems linked to abdominal fat are insulin resistance and the risk of Type 2 diabetes, compromised lung function and migraine headaches. Even asthma risk is raised by being overweight and especially by abdominal obesity, a study of 88,000 California teachers found.

Over all, according to findings among more than 350,000 European men and women published in The New England Journal of Medicine, having a large waist can nearly double one’s risk of dying prematurely even if overall body weight is normal.

All of which raises the question: How best to shed abdominal fat and, even more important, how to avoid accumulating it in the first place?

Chances are you’ve periodically seen ads on the internet for seemingly magical ways to reduce belly fat. Before you throw good money after bad, let it be said that no pill or potion has been scientifically shown to dissolve abdominal fat. You have to work at it. And that means avoiding or drastically limiting certain substances in your diet, controlling overall caloric intake and engaging in exercise that burns calories.

Perhaps the worst offender is sugar — all forms and especially fructose, which makes up half of sucrose and 55 percent of high-fructose corn syrup. One of the best ways to reduce your sugar intake is to stop drinking sodas and other sweet drinks, including fruit juices. Limiting alcohol, which may suppress fat-burning and add nutritionally empty calories, and avoiding refined carbohydrates like white bread and white rice are also helpful.

Make sure your diet contains adequate amounts of protein and dietary fiber, including vegetables, beans and peas and whole grains.

Get enough sleep — at least seven hours a night. In a study of 68,000 women followed for 16 years, those who slept five hours or less were a third more likely to gain 32 pounds.

Finally, move more. In a major national study, inactivity was more closely linked to weight gain and abdominal obesity than caloric intake.