IJE Advance Access originally published online on December 8, 2005
International Journal of Epidemiology 2006 35(1):21-22; doi:10.1093/ije/dyi252
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Commentary |
Commentary: Obesity and mortality—light at the end but still a long tunnel
Center for Human Nutrition, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD 21205, USA
* Corresponding author. E-mail: caballero{at}jhu.edu
The association between obesity and premature death has been recognized (and debated) for almost 100 years. By the 1920s, insurance companies were already charging higher premiums for life insurance coverage to persons with excess body weight, based on their own actuarial data on mortality rates of obese people. But at that time preventing obesity in the US population was far from being a priority public health goal. Through the 1940s scientific and policy focus would continue to centre on insuring adequate intake of essential nutrients and energy, as exemplified by the first release of the Recommended Dietary Allowances (RDAs) in 1941. But the post-war economic boom fostered the era of processed foods, large portion size, television, and the automobile, facilitating the imbalance between higher dietary energy intake and reduced energy expenditure. In the 1950s, President Eisenhower created the President's Council on Fitness to promote physical activity and weight maintenance in the US population. One of the earlier reports on the problem of obesity was released in 1966 by the US Department of Health.1 Shortly after, Jean Mayer reported the results of one of the first school-based obesity prevention programmes in the US.2 Finally, in 1975 the US Senate's Select Committee on Nutrition released the report ‘Nutrition and Health’, warning of the alarming increase in the prevalence of ‘diseases of over-abundance’, listing coronary heart disease, high blood pressure, diabetes, obesity, dental caries, and liver disease.
In this historical context, the 1952 article by Breslow3 may arguably be considered one of the earliest scientific papers advocating weight control as a key strategy to reduce mortality in the US population.
At that time, cardiovascular diseases (CVDs) were the leading cause of death, and Breslow argued that obesity was the underlying factor increasing the prevalence of CVD in the US population. But while the prevalence of obesity (BMI 
30) and of overweight (BMI 25 and <30) has increased dramatically over the past 50 years,4 CVD, a leading cause of death among the obese, has declined. National surveys indicate that risk factors for CVD are indeed less prevalent now than 40 years ago in the obese population. For example, the prevalence of high blood cholesterol (>240 mg/dl) in obese persons has declined by 21% between 1960 and 2000, and similar declines occurred for high blood pressure.5 An exception is type 2 diabetes (T2DM), which has increased consistently as obesity prevalence increased. Furthermore, now T2DM has become common among the paediatric age population, accounting for 
40% of all diabetes diagnosed.6 The progressive reduction in CVD mortality is likely to be dependent on a number of factors, including successful public health campaigns to reduce blood cholesterol by reducing saturated fat and cholesterol intake, anti-tobacco campaigns, and more recently the widespread use of statins to control blood cholesterol levels.
Over 50 years after the publication of Breslow's paper, there is renewed debate on the actual contribution of obesity to premature death in the US population. A recent article by Olshansky et al.7 suggested that the increasing prevalence of obesity in the US is leading, for the first time in its history, to a reduction in life expectancy. In contrast, another recent report found that overweight (BMI between 25 and 30) had no significant impact on mortality.8 And while Breslow argued that obese persons reduced their mortality risk when they lost weight, a recent review on this topic concluded that weight loss had little if any effect on mortality.9 Ongoing trials may shed light on this issue in coming years. Experts recognize that methodological issues are at least one important factor in these conflicting results. Age differences in the sampled population, single vs multiple BMI measurements, diversity of population sampled, small differences in relative risk, and possible measurement errors, have all been mentioned as possible confounding factors. In addition, the nature and strength of the association between BMI and mortality risk appear to vary across populations.10
But the high disease burden associated with obesity is indisputable. Obesity continues to be a major risk factor for high blood pressure, CVD, osteoarthritis, respiratory disorders, gall bladder disease, non-alcoholic fatty liver, and type 2 diabetes. It markedly increases the years of life lost to illness, impacting mainly the younger age and lower socioeconomic level groups.11 As stated by Gregg et al.,5 the US has now a population that is more obese, diabetic, arthritic, disabled, and medicated, but with lower mortality. ‘Breslow, who was always concerned as much about quality of life as about mortality, may not see this as great progress.’
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1 US Department of Health, Education and Welfare. Obesity and Health. No. 1485. 1966. US Public Health Service. Ref Type: Report
2 Seltzer CC, Mayer J. An effective weight control program in a public school system. Am J Pub Health 1970;60:679–89.
3 Breslow L. Public health aspects of weight control. Am Public Health 1952;42:1116–1120. (Reprinted Int J Epidemiol 2006;35:10–12.)
4 Ogden CL, Fryar CD, Carroll MD, Flegal KM. Mean body weight, height, and body mass index, United States 1960–2002. Adv Data 2004;1–17.
5 Gregg EW, Cheng YJ, Cadwell BL et al. Secular trends in cardiovascular disease risk factors according to body mass index in US adults. JAMA 2005;293:1868–74.
6 Hillier TA, Pedula KL. Characteristics of an adult population with newly diagnosed type 2 diabetes: the relation of obesity and age of onset. Diabetes Care 2001;24:1522–27.
7 Olshansky SJ, Passaro DJ, Hershow RC et al. A potential decline in life expectancy in the United States in the 21st century. N Engl J Med 2005;352:1138–45.
8 Flegal KM, Graubard BI, Williamson DF, Gail MH. Excess deaths associated with underweight, overweight, and obesity. JAMA 2005;293:1861–67.
9 Fontaine KR, Allison DB. Does intentional weight loss affect mortality rate? Eat Behav 2001;2:87–95.[CrossRef][Medline]
10 Stevens J, Evenson KR, Thomas O, Cai J, Thomas R. Associations of fitness and fatness with mortality in Russian and American men in the lipids research clinics study. Int J Obes Relat Metab Disord 2004;28:1463–70.[CrossRef][Web of Science][Medline]
11 Fontaine KR, Redden DT, Wang C, Westfall AO, Allison DB. Years of life lost due to obesity. JAMA 2003;289:187–93.
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