BMI and Waist Circumference

BMI and Waist Circumference (WC) are extrapolated from the World Health Organization's (WHO) recommendations and are two of the methods Health Canada and many other organizations use to classify health risk levels. Keep in mind if you are using this system that it does not work for everyone, especially those under 18 and pregnant/lactating women. Other considerations include certain ethnic and racial groups and adults over 65 years of age. Further information is available here.

1. BMI
BMI, or Body Mass Index, is a classification of health risk (not of body fat) developed from collected population data. Since we are looking to start living healthier, one of the key components is ensuring our lifestyles correspond to a low risk of developing health problems. Our BMI helps us determine our ideal weight where this is accomplished.

BMI can be calculated directly by using the formula (weight in kg)/(height in m)². Or by using a straight edge on a Weight vs. Height graph like the one below; your BMI would be the dotted line closest to where your height and weight intersect. Another method is a BMI table, one is pictured below as well. (Or if you're online use a BMI calculator).

Taken from www.healthcanada.ca/nutrition

Your BMI value is then used to classify which BMI Category you fall in, which then has an associated level of risk. These 'risks' I keep talking about include affinity for type 2 diabetes, heart disease, sleep apnea and certain cancers - to name a few. The BMI categories are;

Underweight (BMI < 18.5) - Increased risk
Normal weight (BMI 18.5 - 24.9) - Least risk
Overweight (BMI 25.0 - 29.9) - Increased risk
Obese Class I (BMI 30.0 - 34.9) - High risk
Obese Class II (BMI 35.0  39.9) - Very high risk
Obese Class III (BMI 40.00+) - Extremely high risk

2. Waist Circumference (WC)
Along with BMI, your waist circumference is a very important part of determining your health risks. It helps distinguish between the common body types; such as hourglass, apple and banana. Click here for more information on body types.When fat accumulates around the organs (like in the apple body shape) it is actually more detrimental than when it accumulates elsewhere. It puts pressure on key organs (like your liver) and inhibits optimum performance; thus increasing your risk for health problems.

For women a WC anywhere over 35 inches has increased risk, for men it is a WC anywhere over 40 inches. For instructions on how to take a proper measurement of your waist click here.

3. Using both BMI and WC
When used together, BMI and WC can give you a more accurate evaluation of your health risk levels. BMI can be used in conjunction with your WC only when your BMI is between 18.5 and 34.9. When used together the new risks associated with the BMI categories, if your WC is over the maximum recommendation are;

Normal weight (BMI 18.5 - 24.9) - Least risk Increased risk
Overweight (BMI 25.0 - 29.9) - Increased risk High risk
Obese Class I (BMI 30.0 - 34.9) - High risk Very High Risk

So, keep in mind, if you have a body shape where you tend to accumulate fat around your centre, you may have to a) focus on that area, especially with toning exercises and possibly b) work towards a slightly lower BMI in the 18.5 - 24.9 range to obtain a proper WC.