To the Editor:
In a recent letter in your journal, Walls et al write that “a population approach that de-skewed the population's body weight—reducing most the weight of the heaviest people and leaving largely unchanged the weight of the lightest people—would be particularly safe and effective, but it is not clear how to achieve such a change.”1
We beg to differ, and believe that it is not at all difficult to think of population-wide interventions that affect the obese more than those of normal weight. For example, a tax on energy-dense foods or sugared beverages2 would automatically target the overweight, because this group consumes most of these products. Indeed, it is one of the causes of their overweight. Numerous studies have shown an association between the consumption of sugared beverages and BMI, or between energy-dense foods and BMI.3 This would make a tax on such drinks exactly the kind of intervention Walls et al are looking for, ideally combined with subsidies on healthier foods to prevent decreases in purchasing power decreases among low-income earners. Other examples could be limiting the marketing of such foods, or banishing unhealthy foods from schools. An additional benefit is that, unlike explicitly targeted interventions, such changes to the “obesogenic” environment do not stigmatize obese persons.
We would posit, therefore, that safe and effective interventions that reduce the weight of the heaviest, but not of the lightest people, do exist. In contrast, we cannot think of realistic examples of a population-wide intervention that reduces the BMI of heavy and light people to an equal degree (Walls' scenario 1). The example of the economic collapse in an already poor country (Cuba) hardly counts as a realistic intervention to improve health–though it does seem to have had that effect. Furthermore, as Walls et al show, BMI distributions in western countries historically changed by increasing skewness, not by shifting entire distributions up or down. It is unlikely that interventions that improve diet or increase opportunities for physical activity would do otherwise. The first scenario presented is therefore a bit of a red herring.
In conclusion, unlike Walls et al, we believe it is well known what population-wide actions are likely to be effective. We do agree on the need for rigorous evaluation of the policy experiments that are undertaken, because the effectiveness of such interventions remains largely unknown.4
J. Lennert Veerman
Jan J. Barendregt
School of Population Health
University of Queensland
Brisbane, Queensland, Australia
1. Walls HL, McNeil JJ, Peeters A. Population versus high-risk interventions for obesity. Epidemiology
2. Brownell KD, Farley T, Willett WC, et al. The public health and economic benefits of taxing sugar-sweetened beverages. N Engl J Med
3. Ludwig DS, Peterson KE, Gortmaker SL. Relation between consumption of sugar-sweetened drinks and childhood obesity: a prospective, observational analysis. Lancet
4. Jain A. Treating obesity in individuals and populations. BMJ