Commentary: The importance of addressing the rise of overweight and obesity—progress or lack of action during the last fifty years?

In 1952 Lester Breslow called for action on the new health problem of overweight in the US population. Citing evidence that America's health, based on mortality of white adult males, lagged behind other Western countries, he concluded that the excess premature mortality in US men was closely linked with overweight and that reduction in overweight was accompanied by reduction in mortality. Breslow's1 paper compared differences in mortality rates of men over 45 years of age in the US with men in five other countries; Canada, Denmark, New Zealand, Norway, and Sweden. The age-standardized death rates were significantly higher in the US relative to the other countries, particularly for cardiovascular-renal disease (CVRD) and all-cause mortality. The highest difference was seen between the US and Norway; with US mortality rates over 30% higher. The differences were mostly attributable to CVRD death rates (1852 deaths in the US vs 877 in Norway per hundred thousand men over 45 years). Breslow proposed that excess bodyweight was a key cause of this premature mortality in US men. The paper described the effect of different levels of bodyweight on standardized mortality rates. The analysis, based on actuarial tables of the Metropolitan Life Insurance Company, should be seen as an important first step in establishing the effect of increasing levels of weight on a range of non-communicable diseases. Breslow identified that the definition of ‘normal weight’ then used by the insurance industry was misleading, since chronic disease mortality rates were higher in those considered of normal weight than those considered underweight. He indicated that … ‘even a little overweight; 5–14% above normal, induces a substantially increased mortality rate’, especially in diabetes and cardiovascular diseases. It shows that even in post-war America the average weight based on population normal values was associated with ill-health and excess mortality. Breslow called for the introduction of the term ‘optimal’ rather than normal weight based on a bodyweight associated with lowest mortality rates rather than population means. It is clear that there was already scepticism about the causal link between overweight and disease incidence and mortality in 1952. It was obvious that not everyone who was overweight acquired diabetes and CVRDs. However, data at that time highlighted that incidence for these conditions was higher among overweight individuals. Breslow proposed that a precautionary approach should be taken; suggesting that it was reasonable to recommend that avoiding being overweight would reduce the risk of premature death. This was supported by early evidence of a reduction in mortality risk, observed in overweight individuals who lost weight, analysing data from the Metropolitan Life Insurance Company (1925–34). Insured clients who were overweight had much higher mortality compared with normal weight individuals and were being charged higher insurance rates. Some individuals who lost weight re-applied to the company to have their insurance premiums reassessed. The information presented by Dublin and Marks2 was compelling, finding that the mortality rate in those who had lost weight was lower than the mortality rate in those who remained overweight (hazard ratio of 0.70 for men and 0.74 for women). As consultant to the President's Commission on Health Needs of the Nation, Breslow proposed that overweight was ‘a major public health problem’. He suggested two main approaches should be adopted to prevent this condition; popularizing public health messages on the need to attain an optimal weight; second, evaluating the effectiveness of a range of obesity intervention programmes. He also proposed the need for more research into the relationship between excess weight and increased mortality, and for better measures of overweight itself. Fifty-three years later, it is sobering to reflect on Breslow's recommendations. Most positively it can be seen that scientific understanding of the relationship between overweight and obesity and disease risk has significantly improved. Obesity is now recognized to be associated with an increase in many health problems, some of which primarily impact on quality of life such as exertional breathlessness, musculo-skeletal and skin problems, and infertility, while others increase the risk of premature death, including non-insulin dependant diabetes, gall bladder disease, cardiovascular disease (hypertension, stroke, and coronary heart disease), hepatoesteatosis, and certain types of cancers.3 Severe obesity affects life expectancy; 8.7% of deaths in the UK4 are estimated to be due to excess weight, with life expectancy 9 yrs lower for obese people than non-obese. The health consequences for children are less clear but a systematic review shows that childhood obesity is strongly associated with cardiovascular risk factors and diabetes in childhood, which persist into adulthood, overweight children become overweight adults, and there is significant psychological morbidity.5 It is surprising, however, that Breslow's recommendation to have population guidelines for optimal weight are still limited by the uncertainty of what is an ideal weight to reduce the risk of both all-cause mortality and disease-specific risks. The reasons clearly relate both to the development of improved measures to assess overweight and to the need to understand how these measurements give us a better understanding of the relationship of the health risks associated with overweight at different ages and in different populations worldwide. We are still struggling to define clearly the optimal body weight based on body mass index (BMI) or the usefulness of other surrogate measures of body fat content and distribution. This is illustrated by differences across the life course as the excess health risk associated with increased BMI declines with increasing age.6–9 The shape of the relationship between BMI and subsequent mortality is accepted to be U-shaped or J-shaped in young-aged to middle-aged adults of Caucasian origin, with the lowest mortality observed at values of BMI of 21–23. However, this is less clearly defined above the age of 65 with most studies reporting flattening off at higher BMI values,10–18 or inverse associations,19–22 leading to suggestions that the ideal BMI for older adults is higher than in middle age.11,23 BMI in older people may not be a good measure of fat mass.24,25 The measurement of weight does not differentiate between fat and fat-free mass, and fat-free mass (especially muscle) is progressively lost with increasing age.26 Although, BMI continues to be the most prevalent measure worldwide, the usefulness of additional or alternative measures of body composition or fat distribution such as waist, hip, and arm circumference as predictors of mortality in different groups is not well established with inconsistent results between the few studies that have investigated these.13,20,21,27,28 It is clear that different measures may be more suitable in different populations, age groups, and for different purposes including clinical decision-making, epidemiology, surveillance, and improving public understanding of health promotion messages.29 However, resolution of how we can best measure excess weight still requires a greater understanding of whether the health risks of overweight and obesity are best reflected by measuring excess weight, body fatness, or specifically intra-abdominal fat mass. The uncertainty of measuring disease risks associated with increasing weight also has implications for measuring the total burden of disease attributable to overweight and obesity. For example, obesity attributable deaths in the US have been estimated to range from 112 000 to 414 000 in the year 2000.8,30 The disparate findings highlight the need to continue developing more rigorous approaches for estimating obesity-attributable deaths. Ultimately, though, such studies only serve to better describe a population health problem that is already known to be significant (highlighted by Breslow in 1952). A better understanding of the preventable disease burden caused by obesity may be gained by evaluating public health programmes designed to prevent and treat obesity, something that Breslow also recommended. Recent research has shown that the determinants of overweight and obesity are wide ranging, including worldwide shifts in dietary patterns, the increasingly sedentary nature of modern life, and the effects of urbanization. There have now been a large number of studies and systematic reviews looking at the effectiveness of a range of behavioural and environmental interventions for obesity prevention and management in adults and children. These include interventions of diet, physical activity, education, food production and marketing, environmental change to promote healthy lifestyles, pharmaceutical treatment, and surgery for morbid obesity.31–35 However, such interventions often focus on weight loss. The focus of obesity policies and programmes often overlooks that the ultimate public health goal is the reduction of disease morbidity and mortality caused by overweight and obesity. Obesity interventions should also be evaluated for their ability to reduce non-communicable disease in addition to their impact on reducing body weight. With sufficient knowledge of the effectiveness and cost effectiveness of these programmes, it will be possible to make rational decisions regarding better ways to improve public health. Overall though, Breslow's paper serves to highlight how little progress has actually been made on tackling obesity and its impact on premature mortality in the last half century. Despite the advances in our knowledge of the causes and consequences of overweight, and effectiveness of interventions to prevent and manage obesity, prevalence continues to rise worldwide. A total of 64.5% of US adults are now classified as either overweight or obese, and WHO estimates that 1 billion people worldwide are overweight. Although global health policy has started to recognize the huge impact of the international obesity epidemic, national governments have given little attention, and few resources, to the development of effective multi-sectoral obesity prevention and management programmes. This contrasts with the growing attention to management of chronic diseases, such as diabetes and coronary heart disease, where new integrated models of prevention and care are being developed. Breslow concluded his analysis with the following: ‘Practically every member of the public health team has a contribution to make in developing and applying effective methods for weight control. It is now one of our main responsibilities’. His words are as true now, as they were 53 years ago. What is not clear is how best to ensure that progress is made in stopping the continuing rising trends in overweight and obesity worldwide. Future solutions are likely to require a combined approach involving governments, the food industry, interest groups, and civil society to determine access to healthy food and create environments that facilitate more active lifestyles. It should now be the main responsibility not only of the public health community but also of all sectors of government and society. As we face the urgent need for obesity control and prevention we must address the evaluation of cost effectiveness of our actions or inactions. This will require novel approaches beyond the traditional controlled clinical trial model, testing possible interventions in relation to the environmental context in which they occur.

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