Why is waist to hip ratio important?
February 10, 2017 by
John Quinn - Product Owner - mPort
Your waist to hip ratio (WHR) is a great way to estimate how fat is distributed throughout your body. The lower your number is, the better.
What is Waist to Hip Ratio?
Waist to Hip Ratio (WHR) is calculated by dividing your abdominal waist by your hip circumference. It indicates the prevalence of visceral fat, the dangerous internal fat which coats the organs. The waist circumference is measured at the abdomen level, just above the navel/belly button.
Body shape and fat distribution are important factors when considering health risks associated with obesity. Two people with the same height, weight and total body fat can have very different diagnosis in terms of metabolic function and cardiovascular risk. The main cause of obesity‐related deaths is CVD (Cardiovascular Disease), for which abdominal obesity is a predisposing factor.
To put it another way, adults who store a lot of excess fat around their upper body/waist (i.e. “apple-shaped” bodies) have an increased risk of high blood pressure, type 2 diabetes, heart disease, sleep apnea and stroke, compared with those who have the same amount of body fat stored around their hips and thighs (“pear-shaped” bodies).
There is a wide variety of body fat distribution in both lean and obese adults. Alcohol intake and cigarette smoking are two of of the known, major environmental factors that affect body fat distribution. Genetics and the timing of onset of childhood obesity also play a role in regional fat gain and loss.
Where do we measure Waist Circumference?
When calculating Waist to Hip Ratio, it’s the abdominal waist circumference that’s relevant. This is close to the level of the navel/belly button. The criteria for waist circumference proposed by the World Health Organisation (WHO) is the midpoint between the lower border of the rib cage and the top of the iliac crest (where the larger pelvic bones protrude). The measurement is taken flat (i.e. parallel to the floor). It’s not to be confused with the narrow waist, which is taken at the smallest visible part of the torso.
Posture and other factors affecting the Waist Circumference
The phase of respiration determines the extent of fullness of the lungs and the position of the diaphragm at the time of measurement; it also influences the accuracy of the waist circumference. The WHO STEPS protocol suggests that the waist circumference should be measured at the end of a normal expiration (i.e. after breathing out), when the lungs are at their functional residual capacity (WHO, 2008b).
The tension of the abdominal wall influences the accuracy of the waist circumference measurement. Lowering the tension of the abdominal wall increases waist circumference, whereas increasing the tension (by sucking in) reduces waist circumference. Many individuals unconsciously react to waist measurements by sucking in the abdominal wall; hence, a relaxed posture is best for taking waist measurements. The WHO STEPS protocol recommends advising the subject to relax and take a few deep, natural breaths before the actual measurement is made, to minimize the inward pull of the abdominal contents during the waist measurement (WHO, 2008b).
The amount of water, food or gas in the gastrointestinal tract will affect the accuracy of the waist measurement. One approach is to get measured early in the morning after a good night’s rest.
Classiﬁcations are diﬀerent for men than for women. According to the World Health Organization (WHO), a healthy WHR is under 0.9 for men, and under 0.85 for women.
Classification from World Health Organization (WHO)
Comparison with BMI as a health risk indicator
It’s important to avoid going by BMI alone since it’s not the most accurate form of measurement for lean, fit and healthy individuals who carry additional muscle mass. BMI does not differentiate between body fat and muscle mass, which means it can over/under estimate obesity in some people. A combination of high BMI with a high waist to hip ratio is a much stronger indicator of increased health risk. People with a BMI classification of “Overweight” or “Obese” are in a lower risk category if they also have a low to moderate WHR, compared to those that are in the higher WHR category. Older people (over 75) may find WHR to be a more effective predictor of risk than waist circumference or BMI alone.
If you’re concerned or unsure of how to assess your obesity related health risk talk to your doctor for more information.
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- Waist Circumference and Waist-Hip Ratio – Report of a WHO Expert Consultation (Geneva, 8-11 December 2008): http://apps.who.int/iris/bitstream/10665/44583/1/9789241501491_eng.pdf
- (US) National Center for Biotechnology Information – Role of Body Fat Distribution and the Metabolic Complications of Obesity: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2585758/
- Women, Health & Lifestyle: http://www.women-info.com/en/waist-hip-ratio/
- German Society for Sports Medicine and Prevention: http://www.dgsp.de/
- https://www.healio.com – Waist circumference superior to other fat measures for NALFD risk (Non-alcoholic fatty liver disease and cardiovascular risk)