This systematic review collated seventy-eight studies exploring waist-to-height ratio (WHtR) and waist circumference (WC) or BMI as predictors of diabetes and CVD, published in English between 1950 and 2008. Twenty-two prospective analyses showed that WHtR and WC were significant predictors of these cardiometabolic outcomes more often than BMI, with similar OR, sometimes being significant predictors after adjustment for BMI. Observations from crosssectional analyses, forty-four in adults, thirteen in children, supported these predictions. Receiver operator characteristic (ROC) analysis revealed mean area under ROC (AUROC) values of 0·704, 0·693 and 0·671 for WHtR, WC and BMI, respectively. Mean boundary values for WHtR, covering all cardiometabolic outcomes, from studies in fourteen different countries and including Caucasian, Asian and Central American subjects, were 0·50 for men and 0·50 for women. WHtR and WC are therefore similar predictors of diabetes and CVD, both being stronger than, and independent of, BMI. To make firmer statistical comparison, a meta-analysis is required. The AUROC analyses indicate that WHtR may be a more useful global clinical screening tool than WC, with a weighted mean boundary value of 0·5, supporting the simple public health message 'keep your waist circumference to less than half your height'.

We suggest that a simple, rapid screening tool-the waist-to-height ratio (WHTR)-could help to overcome debates about the use of different body mass index (BMI) boundary values for assessing health risks in different populations. There are six reasons for our proposal: WHTR is more sensitive than BMI as an early warning of health risks. WHTR is cheaper and easier to measure and calculate than BMI. A boundary value of WHTR = 0.5 indicates increased risk for men and women. A boundary value of WHTR = 0.5 indicates increased risk for people in different ethnic groups. WHTR boundary values can be converted into a consumer-friendly chart. WHTR may allow the same boundary values for children and adults. Communicating messages about health risk could be much simpler if the same anthropometric index and the same public health message can be used throughout childhood, into adult life, and throughout the world. This simple message is: Keep your waist circumference to less than half your height.

OBJECTIVE:The normal body mass index (BMI) range, as defined by the World Health Organization (WHO), is quite wide, and some people within this range may have excessive central fat accumulation and elevated metabolic risks. We hypothesize that the waist-to-height ratio (W/Ht), an effective index for assessing central fat distribution among Japanese people, can be used to identify subjects who are at higher metabolic risk within the normal as well as the overweight range. METHODS: We investigated: (1) the values of BMI, waist circumference, and W/Ht in 6141 men and 2137 women at various age intervals and calculated gender (female to male) ratios for all these anthropometric indices; (2) the relation between age and each anthropometric index, between age and morbidity index for coronary risk factors (sum of the scores for hyperglycemia, hypertension, hypertriglyceridemia, hypercholesterolemia, and low HDL cholesterol; one point for each condition if present), and between morbidity index for coronary risk factors and each anthropometric index; (3) the distributions of the subjects, using various proposed indices of waist circumference (those suggested by WHO, the Japan Society for the Study of Obesity, and the Asia-Pacific perspective), and our proposed boundary value, W/Ht 0.5, among the WHO categories based on BMI; (4) the metabolic risks (coronary risk factors, hyperuricemia, high g-glutamyltransferase, and fatty liver diagnosed by ultrasonography), and exercise habits among normal-weight subjects with W/Hto0.5 or Z0.5. RESULTS: (1) For the various anthropometric indices in all age groups, the gender ratio for W/Ht was closest to 1, indicating that a single set of values for W/Ht can be used for men and women. (2) Height correlated negatively with age. Among the anthropometric indices, only W/Ht correlated positively with age for both men and women, while age and all anthropometric indices, except height, correlated positively with the morbidity index for coronary risk factors. For both men and women, the highest correlation coefficient was between W/Ht and the morbidity index for coronary risk factors. (3) Nearly all overweight men and women (BMIZ25) had W/HtZ0.5 (98.5% of men and 97.5% of women). None of the underweight subjects had W/ HtZ0.5. However, 45.5% of men and 28.3% of women of normal weight (BMI 18.5-o25) had W/HtZ0.5. W/Ht, of all the indices investigated, was the best index for signaling metabolic risk in the normal-weight subjects as well as the overweight subjects. (4) Age-and BMI-adjusted odds ratios for multiple metabolic risks, and history of no habitual exercise were significantly higher in normal-weight men and women with W/HtZ0.5 than in others of normal weight. CONCLUSIONS: Waist circumference is improved by relating it to height to categorized fat distribution of different genders and ages. W/Ht is a simple and practical anthropometric index to identify higher metabolic risks in normal and overweight Japanese men and women.

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