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The BMI limits of 20–25 for minimum mortality rates based on US life insurance data set out in the early 1970s were reaffirmed in the 1983 analysis from the London Royal College of Obesity [4] using data from the US Cancer Society that analyzed data on smokers and nonsmokers separately. Therefore, the big issue was whether these limits applied globally. It was hoped that this could be answered with the establishment of the International Obesity Task Force (IOTF) in 1996, but at that time, there was limited longitudinal data on adult weights and heights and their subsequent mortality in non‐Caucasian populations. However, when the IOTF proposed in 1997 cut‐off points of 25 and 30 to define new WHO criteria and set out policies for tackling global obesity, the Japanese delegate desired a lower upper normal BMI cut‐off point of 23.0, whereas the US delegate favored a higher normal cut point of 28.0 despite the original mortality data being derived from the United States. The Japanese argued that setting the upper normal BMI cut‐off point at 25 value did not adequately define overweight in Asian populations, but the United States felt that such a cut point would automatically mean that a large majority of Americans would be defined as overweight which was deemed embarrassing and requiring a rethink of health strategies!

The WHO expert committee decided to continue the long‐standing policy of considering the human race as one entity with ethnic differences being unimportant biologically, so they agreed on a universal upper normal BMI cut‐off point of 25 [5]. However, it was later proposed [6,7] that the BMI lower limit should be 18.5 rather than 20 as there was little evidence at that stage that mortality increased as BMIs fell below 20 and detailed analyses of ill health in Latin America, Africa, and Asia indicated that there were no health disadvantages at this lower level. However, at that stage, data on large populations examining the relationship of BMI to mortality was limited except in India, where it was clear that mortality rose sharply when BMIs were below 16.

Subsequently, because of the intense concern of many Asian physicians about the burden of ill health, especially diabetes, that arose within the supposedly acceptable BMI range of 20–25, a WHO meeting was convened in Singapore. It concluded that there were differences in the relationship between BMI and the health profile as well as body composition when comparing Western populations to data from several Asian countries. Therefore the option of considering an upper BMI limit of 23 was acceptable in Asian countries [8]. China, however, undertook their own extensive analyses when their Chinese obesity collaboration was formed and then concluded that an upper limit of BMI 24 should be suitable for the Chinese [9], but this judgment, as well as the Singapore conclusion about Asians, was geared more to morbidity relationships than to mortality data.