IT'S time to step off the scale and get out the tape measure.

The size of your waist can tell you far more about the state of your health than the number on a bathroom scale. Studies have linked larger waist sizes to higher risk for heart attack, cancer, diabetes, dementia and even incontinence.

Last month, Harvard Medical School researchers reported on a study of 44,000 nurses which showed that even normal-weight women face twice the risk of premature death from heart disease or cancer if they are thick around the middle. Other studies have shown similar risks for men.

The notion of waist size as a barometer of health has been around for years, but the vast majority of doctors still put patients on a scale and calculate their body mass index, which measures weight relative to height.

But many studies of both men and women now suggest that it is not how much you weigh but where you carry your weight that matters most to your health.

In March, an analysis in The Journal of Clinical Epidemiology showed that body mass index is the 'poorest' indicator of cardiovascular health, and that waist size is a much better way to determine, for both sexes, who is at a higher risk for hypertension, diabetes and elevated cholesterol.

Studies suggest that health risks begin to increase when a woman's waist reaches 31.5 inches and her risk jumps substantially once her waist expands to 35 inches or more. For men, risk starts to climb at 37 inches, but it becomes a bigger worry once their waists reach or exceed 40 inches.

However, those numbers are based on averages and are not always useful for very tall or short people, children or certain ethnic groups. Among the Japanese, for instance, health risks start to increase for men with a waist size above 33.5 inches, but for Japanese women, risk does not increase until their waists expand to 35.5 inches.

Last month, The International Journal of Obesity suggested that, particularly for young people, the waist-to-height ratio might be a better indicator of overall health risks. Put simply, your waist should be less than half your height.

But a thick waist does not always correspond with poor health. One extreme example is the Japanese sumo wrestler who, despite his massive size, still might have the cardiovascular health of a slimmer athlete. Sumo wrestlers typically store fat just beneath their skin, where it doesn't cause harm, rather than deeper in their abdomen.

Still, for most people, waist size is important. 'We've known for a long time that people who tend to deposit fat inside their abdomen are the ones who have the highest risk for diabetes and heart attacks,' said Arya Sharma, chairman of obesity research and management at the University of Alberta. 'For most people who are not sumo wrestlers, it's actually quite a good indicator.'

Having a large waist means that you are more likely to have fat around your heart, liver and even ordinary muscles, and it signals that you should be screened for other health problems, like insulin resistance and high cholesterol - particularly high triglycerides.

Losing even a little weight can have a big effect. In a small study, 20 severely obese patients who were put on a very low-calorie diet lost an average of 20 per cent of their body weight. That translated into only a 19 per cent drop in body mass index, but waist size fell 23 per cent. Inside the body, the effect was even greater. Using imaging technology, researchers found that the layer of fat around the heart shrank by an average of 32 per cent, according to a report this month in the medical journal Obesity.

Stress hormones have also been linked to abdominal fat. In one study, researchers used blood and saliva tests to measure the stress response of 67 women, ages 18 to 25, who were subjected to speech and mathematical tasks.

Women who experienced the most stress during the tasks were more likely to have a thicker waist than the women who were not stressed, according to the March report in The International Journal of Obesity.

Doctors say that while diet and exercise can help shrink your waist, most people find it tough to succeed.

If you have a large waist, your first goal should be to stop gaining weight, Dr Sharma said. Exercise and improving the quality of the food you eat will lower your risk for heart and other problems, even if you never lose pounds or inches.

'You might want to focus on being as healthy as you can and not obsess about your weight,' Dr Sharma said. 'Obesity management is not about treating numbers on a scale. It's about improving people's health.' - IHT

This article was first published in The Business Times on May 17, 2008.