Social Structure

• Developed countries have high obesity rates, food deprivation is unusual, and physical activity levels have decreased greatly. Lower income households are reported to feature diets composed of foods that tend to be high in calories and fat - contributors to overweight and obesity - since vegetables, fruits and whole grain cereals are more expensive.
• Developing countries have lower obesity rates, particularly in areas of lower SES populations. People who live in these areas are limited in their ability to provide enough food, have little access to public transportation and engage in moderate to heavy manual labor.

• In many developing countries, obesity co-exists with under-nutrition – a Body Mass Index (BMI) less than 18.5.
• In economically advanced regions of developing countries, prevalence rates of obesity may be as high as in industrialized countries.
• Globally, women generally have higher rates of obesity than men do, although men may have higher rates of overweight.
• Prevalence of obesity in children and adolescents is on the rise in both developed and developing regions.

• Obesity is relatively uncommon in African and Asian developing countries, although when present, it is more prevalent in urban than in rural populations.
• In the region of the Americas, obesity rates for both men and women are increasing in both developed and developing countries as well as countries in transition.
• Many South-East Asian countries are presently undergoing a “nutrition transition” involving a shift in the structure of diet, decreased physical activity and rapid increases in the prevalence of obesity.
• Some countries in the Eastern Mediterranean region report high obesity prevalence in adults, particularly women. The prevalence rates for women in this region are generally higher than for women in most industrialized countries.
• The prevalence of obesity has increased by about 10% to 40% in the majority of European countries over 10 years.
• The prevalence of obesity in the Western Pacific region is highest in the urban areas of the Pacific islands such as Samoa. Although obesity prevalence is low in China, in areas where obesity does exist it is most common among women and in urban areas.

Socioeconomic Transition

• Economic development leads to a shift in BMI in developing countries. As the proportion of under-nutrition decreases, the proportion of the overweight population increases.
• In the initial stages of economic transition, the proportion of people with high BMI’s increase in wealthier sections of society, while among the less wealthy, under-nutrition remains a concern.
• At the mid point of the transition, overweight and underweight can co-exist in the population, presenting a double burden of disease.
• Toward the later stages of the transition, the prevalence of high BMI increases among the poor population.

• Modernization, the growth of industry and technology, was introduced over 50 years ago in the Western world. Modernization has led to an abundance of food (particularly high caloric intake) and a decrease in overall physical activity, contributing to increased rates of obesity.
• Urbanization, population growth in large cities, is associated with changes in diet (more reliance on non-traditional foods) and a more sedentary lifestyle, as shown in Table 1.
• The number of women entering the job market has increased with economic development, and contributed to an increased dependence on convenience foods and the use of labor saving devices such as microwaves.
• Ethnic groups in many industrialized countries appear to be affected by obesity as a result of modernization and urbanization. Genetic predisposition for obesity is suggested to be a factor that only becomes apparent after exposure to a more Western lifestyle. For example:
  • Australian Aborigines have been reported to develop high prevalence rates of obesity, hypertension, and type 2 diabetes after transitioning to a Western lifestyle from their traditional “hunter-gatherer” lifestyle (high physical activity and low-calorie, low-fat, high fiber diet).
  • The Pima Indians of Arizona have a very high prevalence of obesity and type 2 diabetes.Obesity and type 2 diabetes have been found to be less prevalent among Pima Indians living in Mexico compared to Pimas living in Arizona. The Pimas in Mexico have maintained a traditional lifestyle of higher physical activity and a diet including less fat and more complex carbohydrates.
  • Native Hawaiians have demonstrated a reduction in obesity and cardiovascular disease by returning to a traditional diet from a modern diet.

Table 1. The impact of modern society on increased inactivity