In a previous article “Watch Your Belly – not just to look good!” I summarized research showing that an expanded belly is a ticking health bomb and manifestation of deteriorating vitality, as well as reduced physical attractiveness.
Measuring your waist circumference is a good starting point to see where you stand (i.e. to get your baseline) and monitor your progress with exercise and healthier eating. And esthetically, your waist measure tells a lot.
Nevertheless, accumulating research shows that health outcomes are more strongly associated with the ratio of your waist to your height, i.e. the waist-to-height ratio. The waist-to-height ratio is simply the ratio of your waist circumference to your height (abbreviated WHtR). To stay (or become) healthy, as well as physically attractive, make sure your waist circumference is less than half your height.
Cardiometabolic risk
The waist-to-height ratio is a relatively unknown measure, even though the first studies showing that it is an easy and useful predictor of heart disease risk factors were published in the 1990s.[1-7]
The waist-to-height ratio is the best simple indicator of cardiovascular risk and mortality, followed by waist circumference and waist-to-hip ratio.[8] The previously popular BMI is inferior and should not be used for assessment of health risk.[8]
When comparing waist circumference alone with the waist-to-height ratio, the waist-to-height ratio is a significantly better indicator for cardiovascular disease risk, dyslipidemia (cholesterol and blood fat abnormalities), diabetes and high blood pressure, in both men and women, regardless of age and ethnic group.[9] This finding comes from a meta-analysis of studies involving more than 300,000 adults in several ethnic groups.[9]
How your waist-to-height ratio impacts your life expectancy
Your waist-to-height ratio can also give you an idea about how much your body shape can shorten your life. The Health and Lifestyle Survey (HALS) is a prospective study of health and behavior, based on a representative sample of the British population (England, Wales and Scotland).[10] Table 1 shows results from 20-years of follow-up.
Table 1: How the waist-to-height ratio can affect your life expectancy. Numbers represent years of life lost.[10]
|
WHtR |
30 year old
|
50 year old |
70 year old |
|||
|
Man
|
Woman |
Man |
Woman |
Man |
Woman |
|
|
0.5
|
0 |
0.1 |
0 |
0.1 |
0 |
0 |
|
0.6
|
1.7 |
1.4 |
1.4 |
1.4 |
0.5 |
0.8 |
|
0.7
|
7.2 |
4.6 |
5.8 |
4.1 |
2.9 |
2.7 |
|
over 0.8
|
20.2 |
10.6 |
14.3 |
9.2 |
6.7 |
5.9 |
WHtR: waist-to-height ratio
As shown in table 1, for a 30 year old man and woman, a high waist-to-height ratio over 0.8 can shorten life by as much as 20 and 10 years, respectively. For a 50 year old man and woman, a waist-to-height ratio of 0.7 may shorten life by 14 and 9 years, respectively. This study shows that your body shape can have serious consequences beyond mere physical attractiveness.
Waist-to-Height Ratio – keep your waist to less than half your height
To find out your waist-to-height ratio, measure your waist at the level of the navel and divide by your height. You can use either inches or centimeters (as long as waist and height are expressed using the same unit). A waist-to-height ratio below 0.5 is considered ideal. This translates into the health message “keep your waist circumference to less than half your height.” [11] Table 1 shows how to do the calculation for a representative man and women, and how to interpret the risk thresholds.
Table 1: How to calculate your waist-to-height ratio, and effect of “waist loss” on the waist-to-height ratio.
|
|
Man |
Woman
|
|
Waist
|
40 inches |
35 inches |
|
Height
|
5’10 = 70 inches |
5’4 = 64 inches |
|
Waist-to-height ratio
|
40 / 70 = 0.57 |
35 / 64 = 0.55
|
|
Effect of “waist loss” – by exercise and improved food habits – on the waist-to-height ratio:
|
||
|
Waist
|
35 inches |
32 inches |
|
New waist-to-height ratio
|
35 / 70 = 0.5 |
32 / 64 = 0.5
|
The waist measures in table 1, 40 inches for the man and 35 inches for the woman, are the cutoffs for abdominal obesity, according to the American Heart Association (AHA).[12] As shown in the table, this is above 0.5 for a man/woman of average height.
How to interpret your waist-to-height ratio value
As mentioned above, a waist-to-height ratio below 0.5 is considered ideal. A more detailed interpretation of waist-to-height ratio values is given in table 2.
Table 2: Interpretation of waist-to-height ratio values.
|
Waist-to-height ratio
|
Body shape (see illustration below)
|
Comment |
|
0.35 |
you may have visible abs
|
– |
|
0.45 |
you are a healthy pear
|
– |
|
0.5 to 0.6 |
you are a pear-apple |
You have more fat around your waist than is healthy. Exercise more and chose better food options. A value close to 0.6 may indicate that you have testosterone deficiency.[13, 14]Ask your doctor to check your testosterone level.
|
|
above 0.61
|
you are an unhealthy apple
|
The fat around your waist is damaging your health and shortening your life expectancy.[10]You need to start exercising and eating healthier. You likely have testosterone deficiency.[13, 14]Tell your doctor you want to have your testosterone level checked.
|
I will cover the use of the waist-to-height ratio as a screening tool for testosterone deficiency, in an upcoming article.
To give you an idea about how different waist-to-height ratios look, the illustration bellows shows typical body shapes for a range of waist-to-height ratio values.
Look up your waist-height ratio in the Shape Chart
If you don’t have a calculator nearby you can easily look up your waist-to-height ratio “danger zone” in the Shape Chart® below. Just locate your waist and height numbers and see in what zone you end up in. In the Shape Chart® you can also easily see how much you need to reduce your waist to move into a healthier zone.
This Shape Chart® was developed by Dr. Margaret Ashwell, a leading scientist on the waist-to-height ratio and its implications for various health outcomes.
Why divide waist by height?
Why is waist circumference divided by height superior to waist circumference alone?
The waist-to-height ratio is a better proxy of intra-abdominal (belly) fat – and thus health risk – than waist circumference alone, because of the correlations between waist circumference, height, and intra-abdominal fat.[3] For a given waist circumference, shorter people have more dangerous abdominal fat and associated cardiovascular risk factors than taller people.[15] This is why the waist-to-height ratio is a better indicator of your health status than your waist alone.
Applies to everybody, regardless of sex and ethnicity
Aside being the most accurate indicator of health risk, the waist-to-height ratio applies equally to men and women, children as well as young and older adults, and in all ethnic populations.[16, 17] This makes the waist-to-height ratio unique as a screening tool. Both waist circumference and BMI have sex and ethnic specific cut-offs, which complicates their practical use.[16, 18]
It has therefore been proposed that the waist-to-height ratio should be used (instead of waist circumference) as part of diagnosing the metabolic syndrome.[9, 18] Hopefully the next revision of clinical guidelines on the assessment of cardio-metabolic risk will give the waist-to-height ratio the attention it deserves. There is a burning need for education and action to improve preventive medicine efforts worldwide by educating primary care physicians as well as the general population and patients at risk about the dangers of abdominal obesity and of waist-to-height ratio as an easy, reliable way to assess cardio-metabolic risk.[16, 18, 19]
Don’t expect your doctor to tell you
How common is abdominal “belly” obesity? A study that analyzed trends in mean waist circumference and abdominal obesity among US adults 1999-2012 found that the overall age-adjusted prevalence of abdominal obesity increased significantly from 46.4% in 1999-2000 to 54.2% in 2011-2012.[20] This trend in expanding bellies was significant in both men and women, and in all ethnicities.[20]
However, even though more than half of the American population is strolling around with a ticking bomb around their waist, don’t expect your primary care physician to say anything about it. In the Shape of the Nations survey, 100 primary care physicians, 400 people of the general population and 100 patients at risk for cardiovascular disease were interviewed in each of 27 countries using a structured questionnaire.[19] Demographic characteristics were obtained and subjects were asked about their understanding of risk factors, assessment of body weight and body shape, and use of waist circumference to assess cardio-metabolic risk. It was found that on average, 39% of all people visiting a primary care physician worldwide were overweight or obese. In North America, this proportion was 49%.
Abdominal obesity was recognized by 58% of primary care physicians worldwide as a significant risk factor for heart disease; an equal proportion considered high BMI to be a risk factor. Worldwide, 45% of all physicians reported never measuring waist circumference and 52% overestimated the waist circumference that puts their patients at risk.[19]
In the general population, 42% were aware of the association between abdominal obesity and risk, but a higher proportion (60%) considered high BMI an important risk factor. Very few people measured their waist or knew the waist circumference that is considered to confer significantly increased risk. More than half (59%) of at-risk patients had not been informed by their doctors about the link between abdominal obesity and heart disease.[19]
This study clearly shows there is a marked knowledge gap among primary care physicians as well as the general population. It is especially notable that most doctors and people still believe that BMI is an important risk factor. As mentioned above, BMI should not be used for assessment of health risk.[8]
In line with this, a recent study found that the waist-to-height ratio (using the threshold 0.5) identifies far more people at early health risk than BMI and WC used together.[21]
Even at-risk patients aren’t informed by their doctors that their waist is a ticking heart disease bomb. Thus, you have to be proactive and take responsibility for your own health. As a bonus, your physical attractiveness will get a large boost.
Summary
Most people think about their waist in terms of physical attractiveness. And while it is true that your waist can make or break your esthetics, it also has a tremendous impact on your health. Your waist is a barometer of vitality, especially for men, who tend to have larger bellies than women and suffer more health consequences of excess body fat than women do.
Your waist-to-height ratio is the most accurate and simple indicator of your health risk. Start measuring your waist more often and stop obsessing about your body weight. If you get on a serious exercise and healthy eating program, you may lose fat while gaining muscle. This won’t show on the bathroom scale, but your waist measure will. Thus, the ultimate goal for people with a waist-to-height ratio of >0.5 (that means, for the large majority) is to drop inches off your waist. Forget about weight loss! It is “waist loss” that matters! Make “keep your waist circumference to less than half your height” your mantra.
References:
1. Ashwell, M., A new shape chart for assessing the risks of obesity. Proc Nutr Soc, 1995. 54: p. 86A.
2. Ashwell, M., S. Lejeune, and K. McPherson, Ratio of waist circumference to height may be better indicator of need for weight management. BMJ, 1996. 312(7027): p. 377.
3. Ashwell, M., T.J. Cole, and A.K. Dixon, Ratio of waist circumference to height is strong predictor of intra-abdominal fat. BMJ, 1996. 313(7056): p. 559-60.
4. Cox, B.D. and M. Whichelow, Ratio of waist circumference to height is better predictor of death than body mass index. BMJ, 1996. 313(7070): p. 1487.
5. Hsieh, S.D. and H. Yoshinaga, Waist/height ratio as a simple and useful predictor of coronary heart disease risk factors in women. Intern Med, 1995. 34(12): p. 1147-52.
6. Hsieh, S.D. and H. Yoshinaga, Abdominal fat distribution and coronary heart disease risk factors in men-waist/height ratio as a simple and useful predictor. Int J Obes Relat Metab Disord, 1995. 19(8): p. 585-9.
7. Hsieh, S.D. and H. Yoshinaga, Do people with similar waist circumference share similar health risks irrespective of height? Tohoku J Exp Med, 1999. 188(1): p. 55-60.
8. Schneider, H.J., et al., Accuracy of anthropometric indicators of obesity to predict cardiovascular risk. J Clin Endocrinol Metab, 2007. 92(2): p. 589-94.
9. Ashwell, M., P. Gunn, and S. Gibson, 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, 2012. 13(3): p. 275-86.
10. Ashwell, M., et al., Waist-to-height ratio is more predictive of years of life lost than body mass index. PLoS One, 2014. 9(9): p. e103483.
11. Browning, L.M., S.D. Hsieh, and M. Ashwell, A systematic review of waist-to-height ratio as a screening tool for the prediction of cardiovascular disease and diabetes: 0.5 could be a suitable global boundary value. Nutr Res Rev, 2010. 23(2): p. 247-69.
12. Grundy, S.M., et al., Diagnosis and management of the metabolic syndrome: an American Heart Association/National Heart, Lung, and Blood Institute Scientific Statement. Circulation, 2005. 112(17): p. 2735-52.
13. Allan, C.A., et al., Waist-to-height ratio as a predictor of serum testosterone in ageing men with symptoms of androgen deficiency. Asian J Androl, 2011. 13(3): p. 424-31.
14. Svartberg, J., et al., Waist circumference and testosterone levels in community dwelling men. The Tromso study. Eur J Epidemiol, 2004. 19(7): p. 657-63.
15. Schneider, H.J., et al., Measuring Abdominal Obesity: Effects of Height on Distribution of Cardiometabolic Risk Factors Risk Using Waist Circumference and Waist-to-Height Ratio. Diabetes Care, 2011. 34(1): p. e7-e7.
16. Ashwell, M. and S. Gibson, A proposal for a primary screening tool: ‘Keep your waist circumference to less than half your height’. BMC Med, 2014. 12: p. 207.
17. Ashwell, M. and S.D. Hsieh, Six reasons why the waist-to-height ratio is a rapid and effective global indicator for health risks of obesity and how its use could simplify the international public health message on obesity. Int J Food Sci Nutr, 2005. 56(5): p. 303-7.
18. Ashwell, M., Plea for simplicity: use of waist-to-height ratio as a primary screening tool to assess cardiometabolic risk. Clin Obes, 2012. 2(1-2): p. 3-5.
19. Smith, S.C., Jr. and D. Haslam, Abdominal obesity, waist circumference and cardio-metabolic risk: awareness among primary care physicians, the general population and patients at risk–the Shape of the Nations survey. Curr Med Res Opin, 2007. 23(1): p. 29-47.
20. Ford, E.S., L.M. Maynard, and C. Li, Trends in mean waist circumference and abdominal obesity among US adults, 1999-2012. JAMA, 2014. 312(11): p. 1151-3.
21. Ashwell, M. and S. Gibson, Waist-to-height ratio as an indicator of ‘early health risk’: simpler and more predictive than using a ‘matrix’ based on BMI and waist circumference. BMJ Open, 2016. 6(3): p. e010159.
