IJE Advance Access originally published online on December 8, 2005
International Journal of Epidemiology 2006 35(1):16-17; doi:10.1093/ije/dyi267
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Commentary |
Commentary: What's past is prologue
School of Population Health, University of Queensland, Herston Road, Herston Qld 4006, Australia. E-mail: c.bain@sph.uq.edu.au
It is news no longer that we have a waxing size and shape problem, which is beginning to offset health gains of recent decades.1 Need it have come to this? Knowledge of the problem of weight has been with us since Hippocrates time (who is reputed to have written ‘Corpulence is not only a disease itself, but the harbinger of others’), though it was not until the early 1940s, when the Metropolitan Life Insurance Company published its first tables of ‘ideal’ weights, based on the work of Louis Dublin, that a modern epidemiological approach was used to quantify the problem.2
The featured paper by Lester Breslow,3 published 10 years later, seems to be the first alert to a reasonably wide mainstream public health audience, although it had no direct reverberations beyond a single citation in 1955.4 Nonetheless, although Breslow never cited it himself, it seems a likely source—along with his own findings from the Alameda County study5—of his ongoing advocacy of the benefits of maintaining proper weight. As more data emerged from the 1960s on, professional concern spread, and in 1985 an NIH Consensus Conference6 concluded that the evidence for obesogenic harm was overwhelming, but gave no clarion call to action. Even had this been given then, the US was already well into its growth spurt, accelerating from the late 1970s towards having >20% of adults obese by the late 1980s, and topping 30% by 2000.7 Public health eyes were distracted from the notional window of opportunity that Breslow provided by a much hotter agenda. Breslow's own 1954 paper8 on cigarette smoking and lung cancer garnered 113 citations, a fair indicator of where the action was. He was also at the forefront of the contemporary frame-shift away from accepting such age-related diseases as senescent, adding philosophical appeal to the stark public health import of the cigarette story. So the ‘new’ public health of that era can be forgiven for seeming a bit sleepy in its response to the early obesity data. We are now fully awake to the expanding problem, and also alerted to the difficulties ahead by the chequered history of smoking control, nicely encapsulated in a reflective paper by Breslow9: despite the telling data on smoking hazards published in the 1950s and early 1960s, vocal critics kept the issue open until the 1964 Surgeon General's Report provided a cogent causal logic that swayed scientific doubters and gave a strong base for public health action.9 But even with this, and the apparently simple target, smoking remains a major cause of disease in the developed world despite 40 years of concerted efforts at structural and personal levels to limit the habit; and it is driving new epidemics in emerging regions.
Managing a society towards an optimal distribution of weight is even more formidable. The basic issue seems simple—balance the two sides of the energy equation. Many well-nourished children still do, although that is changing.10 Even minor excesses of energy input in the short run magnify over time, and have moved many populations with advanced technology to an undesirable collective weight. Because the shifts needed to reverse this pattern are also small—in the long run—great emphasis has been placed on individuals solving their own equation, either by diet alone, or increasingly by adding to outputs with additional exercise, especially given the independent benefits that may be realized. As individuals we find, though, that both sides of this equation have variable constraints, which can be hard to manage; and as for smoking control, supportive structural and social adjustments are needed. Some external control of the balance may be possible for groups most amenable to collective interventions, such as armed forces and children in schools; and more general initiatives are underway.11 An ambitious multi-pronged legislative attempt to tackle childhood obesity in the US was proposed recently, but did not become law.12 For transitional societies there is the additional tension between the simultaneous needs to increase inputs for the remaining underfed poorest while grappling with emerging over-nourishment, but at least there is opportunity for them to constrain emerging burdens from caloric excess, if resources and circumstances allow.
The massive cost burden of an obesity epidemic13 has attracted a great deal of attention from economists, who offer the only good news (as we might expect from a discipline which has given us the HALY—happiness-adjusted life year14)—speculation that the rise in obesity may be self-limiting.15 While this is too uncertain to allow complacency, the underlying perspective is refreshing and merits attention in planning public interventions. A key point is that our core need is not for more information—we all know the general equation—but rather for effective incentives to change preferences and so make the pursuit of optimum weight more desirable. Too few are willing to pay the present social price, be it effort, dollars or, most notably, forgone pleasures,15 i.e. the need to substitute leisure weight control for job weight control owing to technological advances in the workplace.15,16 Effectively this reflects increased valuation of time, especially for women.17 Parallel advances in electronic entertainment are likely to have played their part too in the rise of juvenile obesity by increasing the attractiveness of sedentary leisure activities, i.e. raising the utility of ‘consuming’ leisure while decreasing its caloric content.16 A smart balance of taxes on calories and exercise substitutes15 and subsidies for exercise might advance both weight control and climate stability; and in the longer run urban planning could have a major complementary role. Finally, mimicking approaches shown to be effective for reducing smoking harm, regulation of the food industry's marketing strategies and taxing ‘dense’ calories18 should be core elements of comprehensive control programmes.
So perhaps even had it been more widely noted at the time, Breslow's paper was not going to avert the problem we now have, but he showed what was coming when few others were concerned. And in many other ways the paper is a fine model for applying epidemiological data and logic to the benefit of public health, one that we can re-learn some lessons from. It is crisply written, makes nice summary use of secondary data to form a compelling community diagnosis in time and place, and considers non-causal explanations for the overweight-disease link. The possibly disparate benefits of true primary prevention, i.e. maintaining ideal weight throughout life (assessed via attributable fraction) and of later intervention to reduce weight are raised, the population prevalence of overweight is estimated to help assess public health importance (population attributable fraction), and both mass and high-risk strategies for control are considered. Finally Breslow identifies specific gaps in the evidence base and exhorts colleagues to engage with this public health challenge. This we now are; and in so doing it will serve us well to give due regard to the practical lessons he draws from his long professional engagement as epidemiologist-activist.9
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