FAT DISTRIBUTION: WAIST-TO-FOP RATIO (WHR) AND WAIST CIRCUMFERENCE
WHR is a ratio of abdominal subcutaneous and visceral fat to hip subcutaneous fat. The measure is ‘anchored’ to a measure around the hips because it had been thought that this was less variable to change. Recently though, Canadian researchers at Laval University in Quebec have suggested that waist measures alone may be sufficient. WHRs (or other ratio measures used, such as waist-to-thigh ratio) generally have a cut-off point determined by epidemiological studies with large populations. Figures of 0.9 for men and 0.8 for women are often used as the cut-off points for WHR beyond which increased disease risk is indicated, but in some studies the figures of 1.0 and 0.9 respectively are used.
Some research has shown that with fat loss in some people, there is a loss from the hips as well as the waist and therefore WHR can remain relatively constant. For this reason it is probably best used as an absolute measure of risk in the first instance of measurement, rather than a relative measure of change, and is best used in combination with other measures such as BMI.
Attempts are currently being made to incorporate WHR and BMI into a single formula, but so far these have not added to the individual predictive value of either single measure. Waist measurements suggested by the Laval group as indicative of disease risk are above 100cm for men and 90cm for women—irrespective of height. Researchers at Glasgow University8 have compared waist measurements with BMI and have come up with the following conclusions for health promotion:
• men with a waist size of > 102cm and women with a waist size of >92cm should be encouraged to lose weight
• men with a waist size of <92cm and women with a waist size of <80cm do not need weight management.
WHR has a relatively high validity in the measurement of abdominal fat distribution, particularly in men and post-meno-pausal women, however validity may be affected by changes in hip size that occur with changes in body fatness. Reliability and sensitivity of waist measures alone is quite high, particularly in the hands of an experienced measurer.
Correct sites for measurement of waist and hips can vary and although there are currently attempts to standardise these, there is still controversy about the correct locations. There is general agreement that hips should be measured at the widest part of the buttocks as determined from side-on. Protocols for waist measurement include measures at umbilicus (the navel), which has the particular advantage of being easy to find, but the disadvantage of being almost at hip level in some obese women. Another waist site is mid-way between the lowest rib and the top of the iliac crest (hip bone), which has the advantage of bony landmarks but does not always capture the large abdominal mass in very obese people. In lean people the waist is the narrowest part between the chest and the hips but in obese people it can be the widest, therefore this is not recommended as a definition. Each has its disadvantages, but provided the measure is used constantly, the actual site becomes less relevant.
WHR and waist circumference measures have the advantages of being quick, non-intrusive and useful for large scale population surveys. WHR has disadvantages in making comparisons between varying groups of people such as is often seen in different cultural groups. Asian women, for example, have small hips and WHR measures are much less valid as an indicator of health risk. Negroid women on the other hand have large hips and buttocks and their health risk may be misinterpreted from WHR measures. Overall WHR, or waist alone, may provide a quick and simple indication of health risk. Waist alone can then be used to examine the success of a fat loss program in those groups where abdominal fat is stored readily.
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