Obesity, diets, and social inequalities

Adam Drewnowski

Obesity and type 2 diabetes follow a socioeconomic gradient. Highest rates areobserved among groups with the lowest levels of education and income and in themost deprived areas. Inequitable access to healthy foods is onemechanismbywhichsocioeconomic factors inuence the diet and health of a population. As incomesdrop, energy-dense foods that are nutrient poor become the best way to providedaily calories at an aordable cost. By contrast, nutrient-rich foods and high-qualitydiets not only cost more but are consumed by more auent groups. This articlediscusses obesity as an economic phenomenon. Obesity is the toxic consequence ofeconomic insecurity and a failing economic environment. 2009 International Life Sciences Institute

INTRODUCTION

Rising rates of obesity in industrialized societies havebeen blamed on increased consumption of sweetenedbeverages and energy-dense foods.1 Published researchhas variously linked rising obesity rates in the UnitedStates to the consumption of rened grains, added sugars,added fats, snacks, beverages, fast foods, and eating awayfrom home.2 One way to change dietary behaviors is bymodifying the obesogenic food environment. Reducingconsumer access to palatable sweet and high-fat foodsseems to be the main goal of many nutrition policies andprograms.

Minorities and the poor are clearly at a disadvantagewhen it comes to the adoption of healthier eating habits.Simply put, fats and sweets cost less, whereas manyhealthier foods cost more.3 Researchers have shown thatlow-income neighborhoods attract more fast-food outletsand convenience stores as opposed to full-service super-markets and grocery stores. By contrast, more auentareas generally have access to better restaurants, fresherproduce, and more opportunities for physical activity.Such studies merely demonstrate that socioeconomicfactors, including inequitable access to healthy foods,have a profound eect on weight and health. It is eco-nomic deprivation that is obesogenic, and one key pre-dictor of weight gain may be low diet cost.

The obesity debate in the United States has steeredclear of the complex issue of social class. Instead, muchtime has been spent on genetics, physiology, race/ethnicity, personal responsibility, and freedom of choice.Some in public health nutrition have adopted the viewthat most Americans could follow a healthy diet butsimply choose not to. Attempts to improve populationdietary habits have therefore emphasized the food-choicebehavior of individuals. The emphasis has been on psy-chosocial factors, self-ecacy, and readiness to change.The unspoken assumption has been that healthful foodsare inexpensive and that allAmerican households, regard-less of income, have access to a healthy diet. It may betime to point out that obesity is an economic issue.3,4

Many segments of society have limited resources and areunable to resist powerful economic forces that are largelybeyond their control.

Americans spend the lowest proportion of dispos-able income on food (~12%) and have the lowest-costfood supply in the world.5 Until recently, no one seriouslyquestioned the benets of low-cost foods or indeed thefreedom to choose. Ocial recommendations and guide-lines, including the 2005 Dietary Guidelines for Ameri-cans, exhorted consumers to choose healthful diets asopposed to unhealthful ones. Other documents recom-mended that obese consumers replace white bread,bologna, and mayonnaise with fresh salads, mangos, and

Aliation: A Drewnowski is with the Center for Public Health Nutrition at the School of Public Health and Community Medicine, Universityof Washington, Seattle, Washington, USA.

Correspondence: A Drewnowski, Center for Public Health Nutrition, University of Washington, Seattle, Washington, 98195-3410, USA.E-mail: adamdrew@u.washington.edu, Phone: +1-206-543-8016, Fax: +1-206-685-1696.

Key words: diet cost, energy density, energy intake, obesity, poverty

doi:10.1111/j.1753-4887.2009.00157.xNutrition Reviews Vol. 67(Suppl. 1):S36S39S36

star fruit. The rapid rise in food prices has helped dem-onstrate that healthier diets are no longer merely a matterof choice.

Food choices are made on the basis of taste, cost,convenience, and, to a lesser extent, healthfulness andvariety.6 Rened grains, added sugars, and added fats aregood tasting, readily accessible, and inexpensive. Low-cost foods and low-cost diets tend to be energy dense andnutrient poor.On one hand they are associated with over-eating; on the other hand they are preferentially selectedby the low-income consumer. The low cost and high pal-atability of energy-dense foods mainly sugars and fats along with the easy access to such foods can help explainwhy the highest obesity rates are found among the mostdisadvantaged groups.3 The key variable, however, is notthe macronutrient composition of the diet; rather, whatmay predict obesity is low diet cost.7

POVERTY AND OBESITY ARE LINKED

The rates of obesity and type 2 diabetes in the UnitedStates follow a socioeconomic gradient, with the highestrates observed among racial/ethnic minorities and thepoor.3 At the individual level, obesity rates are linked tolow income, low education, minority status, and a higherincidence of poverty.8 Among women, higher obesityrates tend to be associated with low incomes and loweducation; the association of obesity with low socioeco-nomic status has been less consistent among men. At theenvironmental level, obesity rates are higher in lower-income neighborhoods, legislative districts, and states.8,9

Although obesity rates have continued to increasesteadily in both sexes, across all ages and all races, and atall educational levels, the highest rates occur among themost disadvantaged groups. Obesity and food insecurity,dened as the limited or uncertain availability of nutri-tionally acceptable or safe foods, also appear to be linked,at least among female recipients of food assistanceprograms.

ENERGY-DENSE FOODS COST LESS

Developments in agriculture and food technology havemade energy-dense foods accessible to the consumer at avery low cost. Figure 1 shows the inverse relationshipbetween the energy density (kcal/g) of foods and theenergy cost (US$/1,000 kcal). Food prices were obtainedin 2006 from supermarkets in Seattle.10 The energy cost offresh produce was 10 times as much as that of vegetableoils and sugars. As indicated by the logarithmic scale, thedierence in energy costs between the healthy andunhealthy foods was several thousand percent. The

energy cost of soft drinks was, on average, 30 cents permegajoule (MJ), whereas that of orange juice from con-centrate was 143 cents/MJ.

Fats and oils, sugar, rened grains, potatoes, andbeans provided dietary energy at minimum cost. Dryfoods with a stable shelf life are generally less costly (perMJ) than perishable meats, sh, dairy products, or freshproduce. The selection of rened grains, added sugars,and vegetable fats may represent a deliberate strategy tosave money. Lower food costs may be associated withmore energy-dense diets, and total energy intake mayactually increase.7 This means that, paradoxically, it ispossible to spend less and eat more, provided that theextra energy comes in the form of added sugar and addedfat.3 The association between poverty and obesity may bemediated, in part, by the low cost and high palatability ofenergy-dense foods.3 In fact, the foods implicated in pro-moting obesity, like snacks, fast foods, sweets, and renedgrains, are those that provide dietary energy at a very lowcost.

The standard dietary advice is to replace fats andsweets with more fruit, vegetables, whole grains, poultry,and sh.1 However, these more healthful foods are alsomore expensive and beyond the reach of many. Somelow-income families limit their food budget to $100 forfour people per week, or less than $4 per person per day.The only foods that can be obtained for this amount ofmoney are high in rened grains, added sugars, andadded fats, and the healthful, recommended foods areseparated by an immense gap in energy costs.

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10

0.1 1 10 100 1000

lardolive oil

lobster

salmon

halibut

margarine

butter crackers

raspberries

milk chocolate

bacon

mayonnaise

lettuce

broccolisugar

white bread

corn tortilla

white rice

banana

peanuts

En

erg

y D

ensi

ty (

kcal

/g)

Energy Cost ($/1000 kcal)2006 retail prices

Figure 1 Relationship between energy density ofselected foods (kcal/g) and energy costs (US$/1,000 kcal). Food prices from Seattle supermarkets, 2006.Note that the energy cost dierential between added sugarsand fats and fresh vegetables and fruit can be several thou-sand percent, as indicated by the logarithmic scale.

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HEALTHIER DIETS COST MORE

Not only do healthier diets cost more, they are also con-sumed by more auent persons. Diet quality in theUnited States is very much a function of socioeconomicstatus. People who are older, wealthier, and better edu-cated are both thinner and have better diets than do thepoor. The impact of socioeconomic status variables ondiet quality has normally been ascribed to a higher edu-cational level or a greater awareness of health issuesamong higher-income groups.One less-explored hypoth-esis is that food choices are driven by the relative dier-ences in cost between high-quality and low-quality foods.This observation is not restricted to the United States:similar associations between higher incomes and higher-quality diets were also found in Canada, France, theUnited Kingdom, and other countries of the EuropeanUnion. A study of the relationship between energydensity and the cost of freely chosen diets in a Frenchcommunity11 showed that dietary energy density wasassociated with higher energy intakes.More energy-densediets were associated with a higher consumption ofgrains, fats, and sweets; there was a negative associationbetween energy-dense diets and consumption of fruitsand vegetables.12,13 In addition, the energy density of thediet was inversely linked to the energy cost.

Replacing fats and sweets with more vegetables andfruits was associated with higher diet costs: each 100 gincrement in additional fruit and vegetable consumptionincreased diet costs.14,15 In contrast, higher consumptionof fats and sweets was associated with a net savings in dietcosts. These data showed that sweets and fats cost less,while low-energy-density diets high in vegetables andfruits cost more.14 InWestern societies, lower energy costsare generally associated with higher energy intakes.

OBESITY: AN ECONOMIC HYPOTHESIS

Food choices by the obese have been explained in terms ofabnormalities in biology, physiology, and behavior.16 Thebiological explanation has been that the observed crav-ings for fats and sweets are driven by central metabolicevents, a serotonin or dopamine imbalance, altered leptinlevels, or the endogenous opiate peptide system. Physi-ological explanations have invoked the glycemic index offoods, individual dierences in fructose metabolism,satiety decits, or insulin resistance. Psychological expla-nations have addressed an addictive personality, acortisol-mediated response to stress, or simply theseeking of comfort in high-fat foods. Environmentalapproaches have blamed the susceptibility of individualsto external cues provided by fast foods or snacks and theinability to regulate calories following the consumptionof soft drinks.

Fewer studies have made the link between the lowcost of energy-dense foods and the obesity epidemic. Thepresent hypothesis is that the links seen between povertyand obesity are primarily attributable to economic vari-ables.15 Unhealthy diets cost less, while the recommendedhealthier diets cost more. As consumers reduce foodexpenditures, their diet becomes increasingly energy richbut nutrient poor.Whereas increasing food expendituresdoes not guarantee a healthy diet, reducing food spendingbelow a certain limit virtually guarantees that the result-ing diet will be nutrient poor and energy dense. House-holds on a limited budget will nd it dicult to eat morehealthfully unless they adopt unfamiliar eating habits,depart from social norms, or eat mostly unpalatablefoods. Public policies to promote dietary change shouldtake into account food preferences and usual eatinghabits.

The growing price gap between healthy andunhealthy foods also supports the causal link betweenpoverty and obesity. The foods that have been found tomaintain their price are fats and sweets, which couldaccentuate disparities in the access that people with lowerincomes have to healthy diets.

CONCLUSION

Given economic constraints, especially among lower-income groups, not all consumers have the same degreeof choice when it comes to purchasing healthful freshproduce, fruit, lean meats, and sh. For many, the choicewas removed long ago by economic and employmentpolicies. There are sound economic reasons why povertyand obesity are so closely linked, and this could aectfuture obesity-prevention strategies. A combination ofagricultural subsidies, pricing policies, regulatory action,and consumer education, involving cooperation amonggovernments, academia, and the food industry, couldfacilitate access to an aordable supply of fresh, nutrient-rich foods. In addition, while the onus to provide low-income consumers with inexpensive, healthy foods iscurrently on the food industry, this view could shift to theneed for policies to address broader societal issues, suchas the falling value of the minimum wage and decliningneighborhood resources. Environmental and policyinterventions will be needed to address the observedinequalities in access to healthy foods, particularly as theyrelate to body weight and health.

Acknowledgment

Declaration of interest. The author has no relevant inter-ests to declare.

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