NUTRITION TRANSITION: WORLDWIDE DIET CHANGE

NUTRITION TRANSITION: WORLDWIDE DIET CHANGE. The world is witnessing rapid shifts in diet and body composition, with resultant important changes in health profiles. In many ways, these shifts are a continuation of large-scale changes that have occurred repeatedly over time; the changes facing lowand moderate-income countries today, however, appear to be occurring very rapidly. Broad shifts in population size and its age composition; in disease patterns; and in dietary and physical-activity patterns are occurring around the world. The former two sets of dynamic shifts are termed the demographic and epidemiological transitions. Dietary and physical-activity changes, reflected in nutritional outcomes such as changes in average stature and body composition, are referred to as the nutrition transition.

Historical Nutrition Patterns

Human diet and activity patterns and nutritional status have undergone a sequence of major shifts, which can be defined as broad patterns of food use and of corresponding nutrition-related diseases. Since the eighteenth century, the pace of dietary and activity change appears to have accelerated, albeit to varying degrees in different regions of the world. Dietary and activity changes have been paralleled by major changes in health status, as well as by major demographic and socioeconomic changes. Obesity emerges early among these shifting conditions, as does the level and age composition of morbidity and mortality. Five broad nutrition patterns have been identified, going back to the origins of modern man. The two "earlier" patterns continue to characterize certain geographic and socioeconomic subpopulations, but much of the modern world is experiencing one or more of three later patterns: receding famine; the appearance of nutrition-related noncommunicable diseases (NR–NCDs); and, in response to these, behavioral change.

Receding famine. In this stage, the consumption of fruits, vegetables, and animal protein increases, and starchy staples become less important in the diet. Many earlier civilizations had made great progress in reducing chronic hunger and famines, but only in the last third of the last millennium did these changes become widespread, leading to marked shifts in diet. Famines continued well into the eighteenth century in parts of Europe, however, and they remain common in some regions of the world. Activity patterns start to shift in this stage, and inactivity and leisure become a part of the lives of more people.

Nutrition-related noncommunicable diseases (NR–NCDs). A diet high in total fat, cholesterol, sugar, and other refined carbohydrates, and low in polyunsaturated fatty acids and fiber, and often accompanied by an increasingly sedentary life, is characteristic of most richer societies (and of increasing portions of the population in poorer societies) in this stage. These characteristics result in increased prevalence of obesity and degenerative diseases that characterize Omran's final epidemiological stage.

Behavioral change. A new pattern appears to be emerging in this stage as a result of changes in diet, evidently associated with the desire to prevent or delay degenerative diseases and prolong health. Whether these changes, instituted in some countries by consumers and prodded in others by government policy, will constitute a large-scale transition in dietary structure and body composition remains to be seen.

Nutrition science is increasingly focusing on these three later stages, in particular on the rapid shift in much of the world's low-and moderate-income countries from the stage of receding famine to the stage of nutrition-related noncommunicable diseases. The concern about this change is so great that, for many, the term "the nutrition transition" is synonymous with it.

Apparent Increasing Rapidity of Shifts in Dietary and Activity Patterns and Body Composition

The pace of nutrition-transition shifts from the receding-famine period to that dominated by nutrition-related noncommunicable diseases seems to be accelerating in poor and developing countries. As use of the term "nutrition" rather than "diet" suggests, the category "nutriton-related noncommunicable disease" incorporates the effects of diet, physical activity, and body composition, rather than dietary patterns and their effects alone. This usage is based partly on incomplete information, which seems to indicate that the prevalence of obesity and a number of other NR–NCDs is increasing much faster in the poor and developing world than it has in the West. Rapid growth in urban populations there is much greater than that experienced less than a century ago in the West. Another element is the shift in occupation structure and the rapid introduction of mass media.

Clearly, there are both quantitative and qualitative dimensions to these changes. On the one hand, changes toward a high-density diet with reduced complex carbohydrates and other important elements, and toward increasing inactivity, may be proceeding faster than in the past. The shift from labor-intensive occupations and physically demanding leisure activities toward less strenuous work and leisure is also occurring faster. On the other hand, qualitative dimensions related to multidimensional aspects of the diet, activity, body composition, and disease shifts may exist. For example, the human diet and every one of these other factors are composed of many components, each of which will affect a person in a range of ways. Eating meat, for instance, will provide humans with many valuable nutrients such as bioavailable iron and vitamin B₁₂ or B₆ not found in plant foods, but also with others such as saturated fat that, when consumed in excess, may harm human health. Social and economic stresses people face and feel as these changes occur might also be included.

At the start of the new millennium, the pace and complexity of life seem to be increasing exponentially. While the penetration and influence of modern communications, technology, and economic systems (related to what is termed "globalization") have been a dominant theme since the late twentieth century, there seems to have been a confluence of changes in these factors that have led to a major global concern about the rapid globalization of the world economy and its impact on various subpopulations.

Increasing access to Western media and the removal of communication barriers enhanced by the World Wide Web, cable television, mobile telephone systems, and other technology are important. The accelerated introduction of Western technology into manufacturing, basic sectors of agriculture, mining, and services is also a key element.

Globalization and China: an example. The types of changes the developing world is facing can be seen in considering life in China in two different periods. During the 1970s food-supply concerns still existed. There was no television, limited bus and other mass transportation, and little food trade. Minimal processed food existed, and most rural and urban occupations were very labor-intensive.

By the end of the twentieth century, work and life in China had changed. Small gas-powered tractors were available, modern industrial techniques were multiplying, offices were quite automated, soft drinks and processed foods were consumed everywhere, televisions were found in about 89 percent of households (at least a fifth of whom received Hong Kong and Western advertising and programming), younger children did not ride bicycles, and mass transit had become heavily used.

Add to such changes similar ones occurring in much of Asia, North Africa, the Middle East, Latin America, and many areas (particularly cities) in sub-Saharan Africa, and it is evident that the shift from a subsistence economy to a modern, industrialized one occurred in a span of ten to twenty years, whereas in Europe and other richer industrialized societies, it took place over many decades or centuries.

To effectively examine the nutrition aspects of these changes, one would need to compare changes in poorer countries in the period from 1980 to 2000 with changes that occurred a half century earlier in the developed world. However, data on diet and activity patterns are not available, and there is only minimal data on nutrition-related noncommunicable diseases and on obesity.

The negative elements of the nutrition transition known to be linked with nutrition-related noncommunicable diseases are obesity, adverse dietary changes (for example, shifts in the structure of diet toward a greater role for higher fat and added sugar contents, reduced fruit and vegetable intake, reduced fiber intake, greater energy density, and greater saturated fat intake), and reduced physical activity in work and leisure. The causes of these elements are not as well understood as are the trends in each of them. In fact, there are few studies attempting to examine the causes of such changes, and there are only a few data sets that are equipped to allow such crucial policy analyses to be undertaken.

Obesity Trends

The most commonly measured health outcome due to shifts in the structure of diet is obesity. Increases in over-weight and obese adults in the developing world since the 1970s have occurred much faster than in richer countries. Shifts in body composition among Chinese adults have been examined (Bell et al., 2001) over an eight-year period. Not only did the average BMI (body mass index, which is the common measure for overweight status and measures weight in kilograms divided by height in square meters) level increase, but the shape of the BMI distribution curve changed over the eight-year period of the study so that there was a large proportion of high BMI adults. From 1989 to 1997 the proportion of underweight men and women dropped considerably, and the prevalence of both overweight and obesity increased greatly, the proportion of overweight or obese men more than doubling and the proportion of overweight or obese women increasing by 50 percent.

China's changes are not unique. Annual increases in the prevalence of overweight and obese adults in selected poor and middle-income countries can be compared with those in the United States. Elsewhere we present data that illustrate the annualized increases from richer countries with comparable data from poorer countries (Popkin, 2002). We also show how quickly overweight status and obesity have emerged in Mexico as a major public-health problem. Compared with the United States and European countries, where annual prevalence increases in overweight and obesity are about 0.25 percent each, rates of change are very high in Latin America. Similar shifts in the prevalence of obesity are found for North Africa and the Middle East and Asia. In each of these countries the annual rate of increase in the prevalence of overweight plus obesity is between 1 and 2.5 (Popkin, 2002).

What is important to note is that increases in the proportion of the adult population who are overweight are far greater in all of these poorer countries than in the United States or most European countries. Only Spain, with its large growth in overweight population in the last decade, is similar, in speed of change, to these countries.

Dietary Changes: Shift in the Overall Structure over Time

The diets of the developing world are shifting rapidly. Good data for most countries on total energy intake are not available, but shifts in the structure of the diet can be examined. Thus, the shift in diet, over time, in the proportion of energy derived from fat has been explored (Guo et al., 2000).

The dramatic changes in the aggregate income–fat relationship from 1962 to 1990 are found in China. Most significantly, by 1990 even poor nations (having a gross national product [GNP] of only $750 per capita) had access to a relatively high-fat diet, which derived 20 percent of its energy from fat; in 1962 the same diet was associated with countries having a GNP of $1,475 (both GNP values in 1993 dollars). This dramatic change arose from a major increase (from 10 to 13 percent) in the consumption of vegetable fats by poor and rich nations alike. Increases (of 3 to 6 percent) also occurred in middle-and high-income nations.

At the same time, there were decreases in the consumption of fat from animal sources for all except the low-income countries. The availability of animal fats continued to be linked to income, though less strongly in 1990 than in 1962. These decreases, combined with the increase in vegetable-fat intake for countries rich and poor, resulted in an overall decrease in fat intake for moderate-income countries of about 3 percent, but an increase of about 4 to 5 percent for low-and high-income countries.

In 1990 vegetable fats accounted for a greater proportion of dietary energy than animal fats for the poorest 75 percent of countries (all of whom had incomes below approximately $5,800 per capita). The absolute level of vegetable-fat consumption increased, but there remained, at most, a weak association of GNP and vegetable-fat intake. Changes in vegetable-fat prices, supply, and consumption equally affected rich and poor countries, but the net impact was much greater on lower-income countries.

There has been an equally large and important shift in the proportion of energy from added sugar in the diets of lower-income countries (Drewnowski and Popkin, 1997).

Examination of the combined effect of these various shifts in the structure of rural and urban Chinese diets reveals an upward shift in the energy density of the foods consumed. Energy intake from foods and alcohol in both urban and rural Chinese adult diets increased over 10 percent between 1989 and 1997. These numbers represent a very rapid shift in energy density. (It is important to note that the Chinese Food Composition Table, from which these data were extracted, measures only a few beverages [milk, coconut juice, sugarcane juice, spirits, beer, wine, champagne, and brandy] and excludes many beverages, in particular tea and coffee, included in normal measures.) Other clinical studies have found that the consumption of higher-density diets is associated with increased total energy intake. Energy density changes in the diet of China, and most likely in other developing countries, are critical components to be monitored.

The Importance of Rapid Social Change, Including Urbanization, Demographic Change, and Behavioral Changes

Diets have shifted far more dramatically in urban than in rural areas. Some critical sociodemographic issues include:

• rapid reductions in fertility that have speeded shifts in age distribution;
• unabated urbanization in Asia and Africa that will leave more of the poor residing in urban than rural areas in future decades;
• economic changes, in particular increased income and income inequality, that appear to define changes in many regions of the developing world;
• globalization of mass media that faces countries at an earlier stage of economic development than in the past.

Urbanization. The structure of diet has shifted markedly as populations have urbanized (Drewnowski and Popkin, 1997). This relationship will, by itself, shift the structure of national diets significantly as the proportion of the population in urban areas grows.

Structural shifts in income-diet relationships. Economists speak of two types of behavioral change. One relates to shifts in the "population composition" of society toward the educated, rich, or urban. The other is "behavioral" and relates to the way people with different characteristics behave, particularly their economic behavior. At the same level of education or income, a person might buy different amounts or types of commodities at different points in time. Research conducted in China shows there have been profound behavioral shifts since the 1980s. For each extra dollar of income, additional high-fat foods are being purchased, when compared with previous years (Guo et al., 2000). This suggests that the demand pattern for food has changed, so that for the same income level patterns of demand are significantly different from those in earlier periods. The explosion in access to goods and exposure to mass media may well have created this situation.

Mass media. There is no doubt that access to modern mass media has grown very rapidly. It is most useful to look at the proportion of households in a country that own television sets. Overall, 88.5 percent of Chinese households owned televisions in 1997. Not only the proportion of people with access to television but also the types of programs and access to Western influences were shifting. In the 1980s cable systems in China did not provide outside programming; by 1997 many provinces provided access to China Star, a Hong Kong system that relies heavily on U.S. and British programming and modern advertising.

While there are not extensive data on the proportions of Chinese households with access to mass media more than thirty years ago, research has shown a marked increase in television ownership and viewing and indicates that media's penetration into Chinese households in 1997 is far greater than into American households fifty years ago, when television was in its infancy.

Health effects. The BMI-disease relationships have been found to vary between major Asian and other subpopulation groups and those of European background. Are these related to differences in the distribution of fat in a body (e.g. fat distributed around the heart and livers in the abdomen versus in the hips and buttocks), or are there underlying equally important genetic factors that account for these differences?

There are a number of different ways these questions could be answered in the affirmative. One is if body composition and other unmeasured racial and ethnic factors affect susceptibility to nutrition-related noncommunicable diseases. Another might be if previous disease patterns (such as the presence of malaria or other tropical diseases) have predisposed the population to certain problems. One component of this might be the fetal insult syndrome hypothesized and popularized by Barker.

A growing body of research shows that international standards used to delineate who is overweight and obese are not appropriate for many large subpopulations. For instance, a BMI of 25 appears to have a far greater adverse metabolic effect in an Asian adult than in a Caucasian adult (Deurenberg et al., 1998). In fact, the World Health Organization (WHO) and the International Obesity Task Force (IOTF) have formed a group of scientists and agencies in Asia to review this topic. This group has held international meetings and has proposed a lower BMI cutoff for Asians, of 23 for overweight and 25 for obesity (International Diabetes Institute, 2000). In one paper comparing China, the Philippines, and U.S. Hispanics, African Americans, and whites, the odds of being hypertensive were higher for Chinese men and women in the 23–25 BMI range than for other subpopulation groups (Bell et al., 2001). Ethnic differences in the strength of the association between BMI and disease outcomes warrant further consideration.

Zimmet and others who have focused on this issue as it relates to lower-income countries have felt that the highest genetic susceptibility for adult-onset diabetes was for Pacific Islanders, American Indians, Mexican Americans and other Hispanics, and Asian Indians. Those groups with modest genetic susceptibility include Africans, Japanese, and Chinese. The age of onset (usually after fifty) of non-insulin-dependent diabetes mellitus (NIDDM) is much lower for these susceptible populations, and it appears that the prevalence is higher for a given level of obesity and waist-hip ratio.

What is not clear is how much of this difference between subpopulations' BMI-diabetes or other BMI-morbidity relationships is a function of differences of body composition, of metabolic or genetic factors, or of social causes. Part of the apparent race-hypertension relationship may also be explained by socioeconomic status (Bell et al., 2001).

There is possibly another factor related to the role of exposure to poor health in this population, for which there is less understanding and no real documentation of its impact (e.g., malnutrition that causes a virus to mutate, parasitic infections that affect long-term absorption patterns, or a parasite that is linked with an unknown genotype—comparable to sickle-cell anemia and its evolutionary linkage with malaria). There is no basis for speculation about the importance of this factor.

The effect of fetal and infant insults on subsequent metabolic function, however, appears to be a critical area. If rapid shifts toward obesity are occurring among those who earlier faced higher levels of low birthweight in a population, then this becomes a much more salient aspect of this argument. In the developing world, where intrauterine malnutrition rates have been and continue to remain high, and nutrition insults during infancy are highly prevalent, research suggests important potential effects on the prevalence of nutrition-related noncommunicable diseases in coming decades (Barker, 2001; Adair et al., 2001). There is an emerging consensus that fetal insults, in particular with regard to thin, low-birth-weight infants who subsequently become overweight, are linked with increased risk of these diseases. Infancy itself, however, may equally be a period of high vulnerability. Three further studies by Hoffman and collaborators (2000) suggest that fat metabolism of stunted infants is impaired to the extent that it could lead to increased obesity and other metabolic shifts. Other work on the role of stunting and obesity (Popkin et al., 1996) had suggested such an effect; Hoffman's work offers the mechanism.

The Coming Cardiovascular Disease Epidemic

Evidence from many developing countries shows that nutrition-related chronic diseases prematurely disable and even kill a large number of economically productive people, a preventable loss of precious human capital. Four out of five deaths from nutrition-related chronic diseases occur in middle-and low-income countries. Reddy (2002) has pointed out that these low-and middle-income countries now account for over three-quarters of global mortality and over 40 percent of the global burden of disease, measured as disability adjusted life years (DALYs) lost, that is attributable to noncommunicable diseases. Among the low-and moderate-income developing countries, the burden of cardiovascular disease alone is now far greater in India and China. Together these two countries account for over half of all new cases of diabetes in the world. Lower-income communities are especially vulnerable to nutrition-related chronic diseases, which are not only diseases of affluence. Such nutrition-related chronic diseases as cardiovascular diseases (CVDs), cancers, and diabetes are becoming major contributors to the burden of disease, even as infections and nutritional deficiencies are receding as leading contributors to death and disability.

Furthermore, cardiovascular diseases in the developing world emerge at an earlier age. Over 45 percent of heart disease–related deaths in low-and moderate-income countries occur under the age of 70 (compared with about 20 percent in high-income countries) (Reddy, 2002).

There are large differences in the profiles of the CVD epidemic across the developing world. Hypertension and stroke, for instance, are more likely to emerge in East Asia, whereas diabetes comes earlier in South Asia.

As would be expected from the dietary and obesity data noted above, CVD levels are far greater in urban areas of the developing world; the opposite is often true in the higher-income developed countries.

The Social Burden of Changes in Diet, Body Composition, and Health

In the richer countries of the world, higher-income groups increasingly follow a more healthful lifestyle when compared to poorer groups. Higher-income Americans consume a more healthful diet, exercise more, and smoke less; similar patterns are found in other high-income countries (Popkin et al., 1996). The prevailing opinion has been that the opposite is found in the developing world, namely, that the poor are less likely to have a heavy burden of nutrition-related noncommunicable diseases than the rich. This statistic is changing rapidly. Monteiro and his collaborators have shown that obesity has gone down among the better-educated, and increased among the less-well-educated, in southeastern Brazil. Soowon Kim and collaborators have shown that not only are less healthful dietary patterns common among higher-income Chinese; so are other harmful dimensions of lifestyle (inactivity, smoking, drinking). Other Chinese scholars have shown a rapid shift in food-consumption patterns among different income groups, which seems to indicate a shift in the burden of unhealthy diets toward poor Chinese (Guo et al., 2000).

The Future

Consuming a more tasteful and richer diet is a goal of most of the world's population. Dietary change is universal; rapid change, though, is now seen especially in the poorest areas of the world. The challenge is to learn how to continue to improve the palatability and quality of our diet, while discovering ways to accomplish this task in a more healthful manner.

See also Food Politics: United States; Food Supply and the Global Food Market; Health and Disease; Nutrients; Nutrition; Obesity; Political Economy.

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Barry M. Popkin