We thank Bradshaw and Stevens (1) for their insightful response to our commentary on the public health implications of the metabolically healthy obesity phenotype (2). This is an important current issue that needs to be debated due to the high burden of noncommunicable disease linked to obesity. Overall, the views expressed by the authors are in accordance with our commentary. For example, their assertion that the solution to the obesity epidemic requires population-level approaches was one of the key messages of our article (2). Moreover, we agree that application of the term “healthy” to the subset of obese persons without metabolic abnormalities is inappropriate, and could result in less attention being paid to the main problem: excess body fat (1). However, several issues raised by Bradshaw and Stevens need further clarification.
First, although body mass index has well-known limitations when applied to certain individuals (e.g., people with high muscle mass), this index is considered a good indicator of body fatness in different racial, age, and sex groups (3). We found that because of its simplicity of measurement and low cost, body mass index is the parameter most frequently used to estimate the prevalence of metabolically healthy obesity (4). Second, regarding the statement that public health will benefit very little from obesity phenotypes, our intention was to debate the importance of obesity in its own right regardless of metabolic health considerations. In brief, given that the metabolically healthy obese are at higher health risk than the normal-weight metabolically healthy, the priority of health professionals should be to promote and facilitate weight loss, regardless of the presence or absence of cardiometabolic risk factors. As we expressed in our commentary (2), this priority does not conflict with the need to ameliorate the various detrimental health consequences of obesity (5). Focusing on specific obesity phenotypes—especially when any obese person will benefit from weight loss—distracts from research and actions needed to reduce obesity levels in the population, as it creates high expectations of a personalized form of medicine for each phenotype. It also provides an excellent argument (i.e., that it is possible to be a healthy obese person) that transnational corporations can use to deter public regulation of their harmful practices (6).
The classic bathtub analogy illustrating the relationship between prevalence and risk may help to illustrate why we claim that more attention should be paid to epidemiologic thinking than to interindividual variation in physiological processes within obese individuals. The public health target must be to reduce the strong flow (new cases of obesity) from the spout. The drain (which represents exit from the population of obese individuals, i.e., successful, long-term obesity treatment) is inadequate for the urgent current needs. The World Health Organization has set a modest goal of leveling off the prevalence of obesity worldwide by 2020 (7). In our view, refinements of the definition of obesity will not help us attain even such a modest target, because they will neither diminish the strong flow from the spout nor increase the size of the drain.
As Sir Austin Bradford Hill stated in 1965, “All scientific work is liable to be upset or modified by advancing knowledge. That does not confer upon us a freedom to ignore the knowledge we already have, or to postpone the action that it appears to demand at a given time” (8, p. 300). We hope that for health professionals and policy-makers involved in obesity epidemiology, both commentaries provide some stimulus towards a new way of thinking about the metabolically healthy obese.
Author affiliations: Centre for Exercise, Nutrition and Health Sciences, School for Policy Studies, University of Bristol, Bristol, United Kingdom (Juan Pablo Rey-López); Department of Preventive Medicine, School of Medicine, University of São Paulo, São Paulo, Brazil (Leandro Fornias de Rezende); Department of Nutrition, School of Public Health, University of São Paulo, São Paulo, Brazil (Thiago Hérick de Sá); and Discipline of Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, Sydney, Australia (Emmanuel Stamatakis).
This work was supported by the São Paulo State Research Foundation (grant 2012/05723-8 to J.P.R.-L.).
Conflict of interest: none declared.