Watching the numbers on scales may not be enough to understand risk factors for obesity-linked disease.

Instead, Tony Ward, a clinical dietician at the King Edward VII Memorial Hospital, said trimming the tummy and calculating your Body Mass Index (BMI) is far more accurate.

He spoke to The Royal Gazette as part of the paper's Have a Heart campaign, which was launched simultaneously with the Live Healthy Bermuda 100 Day Challenge last week.

We want to raise awareness about the problems Bermuda has with obesity, which leads illnesses such as Type II Diabetes and heart disease.

The 100 Day Challenge is a team-based physical activity and weight loss initiative between the Bermuda Diabetes Association, Lindo's supermarket, Aspen Insurance, the Department of Health and Quaker Oats.

At the first weigh-in for the challenge at the Bermuda Underwater Exploration Institute the participants were given their weight, height, percentage of fat and finally their Body Mass Index (BMI). Mr. Ward said: "It's an indication of where you are by using more than weight. But it can be different for different people.

"You could be well and very muscular and be classed as obese. The best way to tell is by your waist circumference because the health risk is around the mid-drift."

The BMI is calculated using both the height and weight of an individual giving a reliable indicator of body fatness for people. (See table)

A BMI of between 18.5 and 24.9 is considered normal while anyone with a BMI of between 25.0 and 29.9 are overweight and anyone with a BMI above 30.0 is obese.

Increasing the health risk, though, is the circumference of a person's waist which should be measured one inch above the hip.

A waist greater than 32in for women and 37in for men increases the risk of cardiovascular diseases, for example, heart attacks and stroke, and diabetes. The greatest risk is for women with a waist measurement of more than 35in and men with a waist measurement of more than 40in.

Using both the BMI and the waist measurements will also eliminate athletes who may fall into the obese category if BMI numbers were used alone.

Mr. Ward stressed, however, that a high BMI cannot be explained away by a bigger frame and that someone who exercises all the time knows if they have more muscle.

He said: "Muscle is four times heavier then fat. So even if you are exercising and you may lose fat in the end you gain muscle so you don't drop your BMI.

"That's why I say people should also pay attention to their waist size."

If readers complete these measurements and find that they are obese Mr. Ward comforted them saying all is not lost. He recommends starting out with small steps such as gardening, walking to work or playing with the children in the yard rather than watching TV to start off your activity.

All of this increased movement will contribute to weight loss and start tackling tummies and BMIs.