The obesity epidemic: looking in the mirror.

This editorial is an invitation to read carefully the issue of Epidemiologic Reviews that accompanies the August 1 issue of the Journal. The focus is obesity. Obesity is an increasingly dominant aspect of the health profiles of adults and children across the globe (1), leading to an urgent need for evidence to support advocacy and for corrective policies and intervention programs targeting an array of societal sectors. The main causes of the epidemic can be stated simplistically: populations are consuming more calories than they are expending and accumulating fat as a result (2). But this story is quite complex. The obesity epidemic has become a metaphor for the adverse health effects of economic and technological advancement. Its multilevel causation extends from genes and individual psychobiology through families to communities to whole societies. Although not of infectious origin as far as we can tell, this epidemic is clearly communicable—moving rapidly in association with globalization within and across populations, of which all appear to be genetically susceptible at some level—and is being transmitted through eating and physical activity, processes indispensable to human survival and social interaction. Epidemiology has contributed to the current societal recognition of the obesity epidemic and its health consequences. Now we need the combined efforts of epidemiologists with varied interests and methodological bents to identify potentially modifiable pathways within the complex picture. To prevent obesity—a top priority for curbing the epidemic— universal solutions reaching entire populations are needed, augmented by initiatives targeted to high-risk groups and individuals (1, 2). Knowing the causes will not necessarily lead directly to solutions. Many causes of excess food intake and inadequate physical activity are embedded in the way we live. Removing high-calorie foods or automobiles from the landscape would be about as infeasible as trying to return to our lean, hunter-gatherer days. The task is to shift some environmental factors in a direction more favorable to achieving energy balance while also fostering individual behavior changes in the same direction (1, 2). The obesity-focused issue of Epidemiologic Reviews is a very welcome addition to the discourse about how to meet the challenges posed by the obesity epidemic. The 12 articles in this issue foster reflection on what we know and don’t know and suggest research opportunities. Caballero’s introductory overview (3) places these issues in historical perspective, reminding us of the not too distant past when the focus of international nutrition efforts was on ensuring production of sufficient food to combat hunger and malnutrition worldwide. Now, concern about excess food consumption must also be considered of paramount importance. Caballero traces the societal changes that have led to the emergence of the problem of prevalent obesity in many countries and, in some countries, to the ‘‘dual burden’’ of coexisting obesity and undernutrition in the same households or communities. Several of the reviews relate to prevention—documenting the status of the problem to clarify what is needed and providing clues about where to look for solutions. Wang and Beydoun (4) quantify a possible future scenario for obesity in the US population. They project that 75 percent of adults will be overweight (body mass index 25 kg/m) or obese (body mass index 30 kg/m) and that 41 percent will be obese by 2015. Projections for children and adolescents are that the body mass index levels of one in four will be at or above the 95th reference percentiles. Childhood obesity causes morbidity during childhood and predisposes to obesity in adulthood. Kelishadi’s account of the prevalence of obesity and the metabolic syndrome among children in developing countries (5) leaves us with an even greater sense that we must find definitive solutions, and quickly. Obesity prevalence is increasing rapidly among children in many developing