produced in Europe about 23,000–25,000 years ago. These ancient individuals may well have had a severe form of genetic obesity, and Bray suggests that they may have been considered deities – this would not have seemed unreasonable in societies constantly striving to avoid food shortages. This predicament might still have applied to the general population in the early agricultural period 5000–6000 years BC in Mesopotamia and later in Egypt, but by then, with greater food availability, obesity was particularly seen in the ruling classes. However, Bray points out that by then, obesity was considered objectionable rather than reflecting a remarkable and unusual status akin to that of a deity. These individuals most likely suffered from not only the common problems of backache and arthritis but also the impact of comorbidities such as diabetes. Chinese and Indian medicine also dealt with obesity as a problem condition, and the particular propensities for Asians and the people of the Middle East to display ill health on weight gain are discussed later. Further on the Roman Galen distinguished between “moderate” and “immoderate” obesity, so in a European rather than an Asian or Middle Eastern context, there may have been a sizable number of overweight individuals with few complications, whereas others were handicapped by their adiposity without this automatically being a reflection of the degree of obesity.
In this ancient literature, it was clear that obesity was considered a clinically unusual event, and so it is little wonder that the original classification of diseases being steadily developed in France during the 19th century included obesity along with other clearly identified clinical abnormalities, some of which were only really apparent on postmortem examination. This classification of diseases was taken over by the World Health Organization (WHO) on its formation in 1948, so in practice, WHO recognized obesity as a disease entity from its inception. However, at this stage, WHO’s primary focus was public health with a heavy emphasis on the poorer countries of the world at a time when obesity was not a problem in lower‐income countries.
Obesity as a public health problem
It is commonly perceived that obesity has only recently been recognized as a public health issue and its potential impact on population health is still yet to be completely acknowledged. However, in his book titled “Fat in the Fifties,” Rasmussen [2] describes a period in post‐World War II America when obesity was being described as the greatest threat to public health. During the 1940s, heart disease replaced infectious diseases as the major cause of death in the United States. At the same time, data from insurance companies identified that higher body weight (relative to height) was associated with an increased risk of premature death, including those from heart disease, and thus obesity was defined as the major public health concern to be addressed. In the 1950s, research by Keys and his colleagues suggested that the three major risk factors for coronary heart disease (CHD) were smoking, high blood pressure, and a high plasma cholesterol level. These findings were seized upon and promoted by vested interests such as the sugar industry that were threatened by the suggestion that excess calories were driving the rise in heart disease and cancer. Although it was recognized that weight gain increased both blood pressure and blood cholesterol levels but obesity per se did not seem to be nearly as important as an independent predictor; in Key’s analysis, the olive oil eating, fatter Greek men had one of the lowest CHD rates. As a consequence, obesity lost its prominence as a key public health issue and was buried by the avalanche of concern around what was then described as the “true” risk factors for heart disease.
Obesity was again raised as a serious public health issue in the early 1970s. One author (W.P.T. James) was involved in producing the UK report on obesity for the UK Department of Health and Social Services and the Medical Research Council [3]. At that stage, obesity was being defined as a percentage excess weight above the desirable weight for height listed by the US Metropolitan Life Insurance Company in complex tables with weights in clothes for three personally chosen frame sizes. These figures relating to pre‐Second World War mortality statistics that were collected on millions of insurance‐eligible Americans. The UK report wanted a standardized measure of body weight that would account for people of different sizes and adopted the approach of the Belgian mathematician Quetelet’s from 1835, who recommended that this could be best achieved deriving the index W/H2 in metric units; a unit now termed the body mass index (BMI). It became apparent that when taking the insurance tables and then considering only the lower limits of the small frame size and the upper limit of the large frame size that the derived Quetelet index was almost the same across a huge range in heights. This ideal body weight from the insurance tables translated into an index of 19.1–24.6 for women and to 19.7–24.9 for men after adjusting for the weight of light clothing and shoe heights. John Garrow, a member of the committee, then rounded these numbers for clinical use to BMI of 20–25. Based on the insurance company’s approach of specifying obesity when weights were 20% above ideal, obesity cut‐off was set at BMI 30.
Lower limits of BMIs in non‐Caucasians?
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.
Morbidity burden starts at much lower BMIs
The setting of these cut points has led many clinicians to assume that a BMI between 20 and 25 is optimum as the mortality risk is minimum. However, it has been known for decades that the risk of diabetes increases progressively from a BMI of about 20, and in the United States is then 5 times higher in women before the BMI of 25 is reached [10]. Furthermore, the incidence of hypertension and increases in blood cholesterol levels, and the risk of both cardiovascular diseases and colon cancer show linear increases
