According to Statistics Canada, 61.3 per cent of adult Canadians were overweight or obese in 2015, says an article in the Canadian Medical Association Journal (CMAJ August 31, 2017). That means three in five Canadians are overweight or obese.
In 2015, the percentage of those who were obese rose to 26.7 per cent, up from 23.1 per cent in 2004. Obesity has continued to increase in adult men and women who are age 60 years and older.
Researchers warn us focusing on body mass index (BMI) misses the risks of high body fat in people of normal weight.
BMI is a person’s weight in kilograms divided by the square of height in meters. BMI does not measure body fat directly. But BMI is an inexpensive and easy-to-perform method of screening for weight category.
Your BMI may be normal for your height and weight but you may still have more fat than is good for you. It may misclassify someone who is short and muscular.
On the other hand a high BMI can be an indicator of high body fatness.
BMI can be used for population assessment of overweight and obesity. Because calculation requires only height and weight, it is inexpensive and easy to use for clinicians and for the general public. BMI can be used as a screening tool for body fatness but is not diagnostic.
How is BMI interpreted for adults (over age 20)?
- BMI below 18.5 – underweight
- BMI 18.5 to 24.9 – normal or healthy weight
- BMI 25.0 to 29.9 – overweight
- BMI 30.0 and above – obese
The question is – Is BMI the best way to measure obesity?
The CMAJ article says, “A provincial spokesperson for Manitoba (where child obesity is climbing) questioned the value of the measurement because BMI does not consider lifestyle behaviours like dietary quality, physical activity, which are, in fact, stronger determinants of death and disease.”
The CMAJ article goes on to give many examples where BMI may not accurately reflect a person’s risk of serious obesity related illnesses. Incidence of coronary heart disease, stroke, cancer and type 2 diabetes is higher in overweight and obese person.
A recent study in Frontiers in Public Health (July 24, 2017) by Philip B. Maffetone and colleagues say using BMI to measure obesity likely underestimates the problem. They propose measuring a person’s waist instead of their weight to assess health risks. Abdominal fat or obesity has more severe health effects than fat in other parts of the body.
A person has to reduce abdominal girth to reduce adverse health risks. A person’s waist should be less than half their height. This waist-to-height ratio may be the single best clinical indicator of health risk as it can be used throughout childhood, into adult life, as well as throughout the world.
Most clinicians usually know if the patient in front of them has too much body fat. They should not have to wait for the latest consensus to encourage lifestyle changes: lose weight, make dietary quality changes and increase physical activity. Simply put… eat less and exercise more.
Start reading the preview of my book A Doctor's Journey for free on Amazon. Available on Kindle for $2.99!