Most of us know that obesity is where a person has high levels of body fat, but at what point does overweight become obese? There are different ways of determining this and one way that many people are familiar with is the Body Mass Index.
Body Mass Index (BMI) classifies whether a person is overweight or obese by looking at their weight to height ratio. It is calculated by taking a person’s weight (in kilograms) and dividing it by their height (in meters squared).
BMI= weight (kg) / height (m) x height (m).
People are considered overweight if their BMI is between 25 and 29.9 and obese if it is above 30.
There are different levels of obesity, too. For Caucasians*:
Class I obesity is a BMI between 30 and 34.9.
Class II obesity is a BMI between 35 and 39.9.
Class III obesity (also called morbid obesity) is a BMI is greater than 40.
*There is a different scale for those of Asian and South Asian ancestry, which is approximately 5% lower.
Research has found that waist-to-height ratio is a much better predictor than Body Mass Index (BMI) of cardiovascular health risk such as heart attack and stroke, as well as a shorter lifespan due to other illnesses.
A meta-analysis from 2012 pooled data from multiple studies, and examined Waist to Height Ratio (WHTR) in more than 300, 000 adults from several different ethnic groups and found that was a far better predictor of cardiovasular of metabolic risk factors in both men and women, than BMI [1].
A 2014 study found a correlation between Year of Life Lost (YLL) for different values of Waist to Height Ratio (WHtR) and found that YLL increased dramatically in both males and females when above 0.52 – a waist circumference of just over half one’s height [2].
*Both males and female non-smokers have a slightly increased Years of Life Lost at waist circumference > 0.50, even when their BMI was in the normal range (18.5 to to 22) – which means that waist circumference is a more important predictor of shortened lifespan due to cardiovascular disease, than BMI.
Determining Waist to Height Ratio
If you’re a male and 5’10” tall (70″ tall), then to be in the lower risk category, your waist circumference should be 35 inches or less.
If you’re a female and 5’6″ tall (66″ tall), then your waist circumference should be 33 inches or less.
But where should we measure waist circumference?
Is it where we wear our pants? Is it at the smallest part of our belly, where it dips in? Is it where our navel (belly button) is? Each one of these will produce very different results.
Measuring Waist Circumference
For the purposes of calculating risk associated with carrying excess weight around the middle, waist circumference and hip circumference need to be taken at very specific locations, as described below.
Using a flexible seamstress tape measure, stand in front of a mirror so that you can see both the front and back of where you are placing the tape measure.
It is also important that your belly is completely relaxed when taking the measurement, not sucked in. One way to do that is to taking a deep breath and let it out fully just as the measurement is taken.
Take your waist circumference at the midpoint (i.e. half way) between your lowest rib and the top of your hip bone (called the ”iliac crest”) — being sure that the tape measure is perpendicular to the floor (i.e. not higher in the back or the front).
Looking at the graph above, one can see that for every little bit over 0.5, the risk rises steeply.
Where to Measure Hip Circumference?
Hip circumference is also needed for other assessors, including the waist to hip ratio. Measuring hips should be done at the widest part, making sure the tape measure is the same height in the front and the back.
How Much Should I Weigh?
People often ask me “how much should I weigh” – wanting me to provide them with a specific weight in pounds, or kilos. My usual answer is that when your waist circumference is half your height and your lab test results are optimal, everything else is aesthetics (what you look like). While I can provide a ball-park figure based on height and weight, how much people should weigh is better determined by them having the lowest risk of heart attack or stroke (cardiovascular disease) and the lowest amount of Years of Life Lost.
Health is not a number on the scale. Its the measurement of the amount of fat in our abdomen, around our liver, kidneys, pancreas and heart.
If your waist circumference is greater than 0.5 you are at risk. If you have been diagnosed with type 2 diabetes or pre-diabetes, high blood pressure or high cholesterol, then this risk is compounded. Add to that a family history of these metabolic diseases, and your risks are even higher.
While we can’t change our family history, we can change our diet and lifestyle and lower our risk.
Attaining a waist to height ratio of 0.5 is often associated with lower blood sugars, lower blood pressure and better cholesterol – even more so when the diet to achieve the weight loss is intentionally designed for these outcomes.
If you would like help getting on your own road to better health, please send me a note using the Contact Me form on this web page, and let me know how I can help.
To our good health,
Joy
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https://www.facebook.com/lchfRD/
References
- Ashwell M, Gunn P, Gibson S (2012) Waist-to-height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors: systematic review and meta-analysis. Obes Rev 13: 275—286
- Ashwell M, Mayhew L, Richardson J, Rickayzen B (2014) Waist-to-Height Ratio Is More Predictive of Years of Life Lost than Body Mass Index. PLoS ONE 9(9)
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