Urgency of reassessment of role of obesity indices for metabolic risks

The definition of metabolic syndrome places emphasis on health care for persons at risk. However, whether an obesity index should be a mandatory component of the definition and whether obesity indices can identify metabolic risks satisfactorily require further exploration. Therefore, we investigated the effectiveness of various anthropometric obesity indices in identifying the clustering of 2 or more American Heart Association (AHA)/National Heart, Lung, and Blood Institute (NHLBI)/International Diabetes Federation (IDF)-defined metabolic risk factors (hypertension, hyperglycemia, hypertriglyceridemia, and low high-density lipoprotein cholesterol) for metabolic syndrome and those of other metabolic risk factors (high low-density lipoprotein cholesterol, hyperuricemia, high γ-glutamyltransferase, fatty liver) in 6141 men and 2137 women. The anthropometric indices were the following: (1) for both sexes—various levels of waist-to-height ratio (WHtR) including 0.5 and body mass index (BMI) of 23 and 25 kg/m²; (2) for men and women individually—waist circumference (W) 90/80 cm (AHA/NHLBI/IDF for ethnic groups), W 85/90 cm (Japan Society for the Study of Obesity), and combined W and BMI: W 85/90 cm and/or BMI 25 kg/m² (Japanese government). The results showed the following: (1) The optimal value for WHtR was 0.5 for AHA/NHLBI/IDF-defined risk factors and approximately 0.5 for other risk factors in both sexes. (2) The sensitivities of various proposed obesity indices for identifying clustering of defined and other risk factors varied between 74.4% (WHtR 0.5) and 36.3% (BMI 25) and between 80.5% (WHtR 0.5) and 43.7% (BMI 25) in men, and varied between 65.6% (WHtR 0.5) and 16.8% (W 90 cm) and between 82.3% (WHtR 0.5) and 28.2% (W 90 cm) in women. Because the sensitivities of many anthropometric indices were very low, a reassessment of the effectiveness of obesity indices in evaluating metabolic risks and especially their suitability as a single mandatory component of metabolic syndrome is urgently needed. However, WHtR 0.5 provides a very useful algorithm for screening persons at risk.