A tape measure around the waist helps show who is at risk for heart disease beyond standard body-mass-index measurements, but not all family doctors are routinely using it.

Scientists are learning more about how the deep abdominal fat that surrounds vital organs is worse than fat just beneath the skin in terms of risk of developing heart disease, Type 2 diabetes and other obesity-related illnesses. That's why waist circumference is important to watch for the 65 per cent of Canadians adults who are overweight or obese.

"When your waist circumference is bigger, all that fat is around all your organs," said Grant Barber, who is participating in a study on weight loss through exercise at Queen's University in Kingston, Ont. "For some reason, I never thought of it that way before, and it kind of gave me a visual as to 'That can't be good.'"

Waist circumference how-to

Body mass index (BMI) and waist circumference (WC) are both used to identify whether you are at increased risk of developing health problems because of your body weight or shape. BMI is based on measurements of height and weight and is not a direct measure of body fat, while waist circumference indicates health risk associated with excess abdominal fat. BMI works better for some ethnic groups than others.

Waist circumference is measured at a point halfway between the hip bone and lowest rib — about five centimetres above the belly button.

Many people think the hip bone they feel toward the front of the body is the top of their hips but it's not. By following this spot upward and back toward the sides of your body you should be able to find the true top of the hip bones.

Wrap the tape measure around you in a circle, making sure it is level all the way around. The tape shouldn't push in or indent the skin. Relax, take two normal breaths, exhale, and then take the measurement. It's best to take the measurement on bare skin. If you wear clothes, measure it the same way each time.

A waist circumference of more than 102 centimetres (40 inches) for men and more than 88 centimetres (35 inches) for women is associated with increased risk of Type 2 diabetes, coronary artery disease, and hypertension.

A healthy waistline is 94 centimetres (37 inches) for most men and 80 centimetres (31.5 inches) for women. Health Canada recommends measuring waist circumferences for adults with a BMI between 18.5 and 34.9 to prevent and manage obesity.

Sources: Health Canada, Alberta Health Services, Heart and Stroke Foundation of Canada, Canadian clinical practice guidelines in management and prevention of obesity

Using waist circumference alongside BMI helps doctors, nurses, dietitians, kinesiologists and psychologists to tease out who is in greater need of weight-loss counselling, said Prof. Robert Ross, an exercise physiologist at Queen's.

A healthy waistline is:

  • 94 centimetres (37 inches) for most men.
  • 80 centimetres (31.5 inches) for women.

Research suggests that if the waist circumference climbs to more than 102 centimetres (40 inches) for most men or more than 88 centimetres (35 inches) for women then the risk of Type 2 diabetes, coronary heart disease, and other obesity-related illness also rises.

Watchful on waist

Those risks explain why Canadian family doctors are encouraged to watch their patients' waistlines.

"It would put people potentially in a different risk category if their waist circumference was above the cutoff," said Dr. Karl Iglar, an associate professor of family medicine at the University of Toronto. "It might lead to lifestyle interventions at an earlier stage than with BMI alone."

In 2007, waist circumference became part of a preventive care list for family doctors in Canada — a checklist for physicians to use during checkups for adults that also includes measures like colonoscopy and hepatitis B screening.

While it's simple for doctors to wield a tape measure alongside their prescription pads, there is room to improve on their use of the tool, said Iglar, who developed the checklist. Impediments to greater use may include the time required, uncertainty about who should take the measurements, and a lack of familiarity with methods, Iglar suggested.

Since a healthy diet and exercise can shrink the waist while weight stays the same, a smaller waist circumference may reflect health improvements from lifestyle changes that might otherwise be abandoned by those discouraged by numbers on the scale that barely budge, Ross said.