Index of central obesity - A novel parameter

Abstract

Waist circumference (WC) is globally used as a parameter to quantify central obesity, the key culprit in insulin resistance and related disorders. Hitherto globally in various definitions of metabolic syndrome and risk scores, WC is used to quantify central obesity. For defining central obesity, which is a single entity numerous WC cutoffs have been suggested, separately for males and females and various races. We believe that this difference is amenable to differences in their average heights. To quantify proportion of visceral fat in the total body fat, WC alone is not sufficient. We hereby hypothesize that Index of central obesity (ICO) defined by us, as a ratio of WC and height is a better parameter of central obesity. If ICO is used in place of WC we may do away with various WC cutoffs and may have a single cutoff applicable to all races and both genders. Using average heights of various countries and their respective WC cutoffs suggested by IDF consensus definition for defining metabolic syndrome (MS) we derived their ICO cutoffs mathematically. The ICO cutoffs obtained ranged from 0.51 to 0.58 among males and 0.47 to 0.54 among females. The range has narrowed down compared to wide range of cutoffs for WC i.e. 90-102 cm for males and 80-88 cm for females. To test superiority of ICO over WC even among people of same race and same gender we conducted a pilot study in which, we compared two subjects with same WC and body mass index (BMI), though they differed in their stature. Body fat distribution was compared on DEXA and oral glucose tolerance was tested. Percentage of total body fat contributed by truncal fat was 36.11% in taller subject (Dr. P) and 46.31% in the shorter one (Mr. P). On investigation Dr P had normal glucose tolerance while Mr. P was diagnosed to be diabetic. These differences unexplained by identical WC and BMI could be explained by difference in their ICO (0.557 vs 0.645). ICO has a potential to be a better parameter of central obesity. It may obviate the need for numerous WC cutoffs and may even be applicable to children where existing parameters are not useful.