Obesity is the most important risk factor for the development of diabetes. In Mexico, studies based on a cross-sectional study in 1992 and the National Health Survey of 2000 showed that increased BMI and waist circumference are more common in people with
diabetes (Aguilar-Salinas et al., 2003; Aguilar-Salinas et al., 2002; Vazquez-Martinez et al., 2006); and even more common in adults under 40 years old when compared to adults over 40 years old (Aguilar-Salinas et al., 2002).
Studies in developed countries have concluded that unhealthy behaviours such as poor diet, physical inactivity and obesity occur more frequently in adults with lower SES (Brunner et al., 1997; Marmot et al., 1991; Metcalf et al., 2008; Rathmann et al., 2006).
This may be due to the more educated being more likely to make choices on nutrition requirements (Geyer et al., 2006). Moreover, in environments where healthy food is costly only persons with a higher income may be more likely to access it. Alternatively, current income and occupation may determine where people settle which in turn
determines which environmental risks people are exposed to. Therefore, individual and family socioeconomic status may play a role in diet and residence choices.
Some evidence indicates that lifestyle choices such as physical activity and diet are consequences of social and economic development, modernization and urbanisation.
For instance, it has been observed that individuals living in rural areas are less sedentary and have a lower prevalence of obesity (Ali et al., 1993; Herman et al., 1995). Because western and industrialized societies experience higher increases in obesity, inactivity and population ageing, it is in these societies that there is an increased prevalence of diabetes (Winer et al., 2002). Therefore, demographic and epidemiological transitions partly explain the association between diabetes and SES. According to Popkin (2002), as countries develop economically and go through a process of urbanisation and industrialization, they advance to a stage of the epidemiological and nutritional transition characterized by high prevalence of obesity and chronic and degenerative diseases. Hence, socioeconomic development leads to changes in lifestyle which in turn increase the risk of diabetes: more sedentary jobs and sedentary leisure activities that occur parallel to the increased consumption of diets high in calories and fat.
The concepts of “risk regulators” (Glass et al., 2006), “ecological factors” or “place effects” (Brown et al., 2004; Macintyre et al., 2002; Pickett et al., 2001) have emerged to describe social influences on individual action. Risk regulators include: cultural norms (such as food preference and body image norms); area deprivation (such as poverty and overcrowding); psychosocial hazards (such as crime and social
disorganization); built environments (such as connectivity and places to walk); physical environment (local food environment: presence of fast food and availability of healthy foods); social environment (social networks, psychosocial stress); economic (systems of food distribution, policies and pricing, food prices and taxes, economic insecurity); and commercial messaging.
For instance, a healthy environment is that where there is access to affordable and healthy food and there are places to exercise: parks, recreational spaces, or sport facilities. Exercising in public areas may be encouraged by safe neighbourhoods or transportation, or discouraged by stressful conditions such as high density, noise and traffic. If health care facilities are present in the area, health information and prevention programs may pursue healthy behaviours in the population (municipal services).
Cultural factors may determine lifestyle and preferences (such as the preparation and consumption of food), (Murcott, 1982); and norms and attitudes towards physical activity (Ramanathan et al., 2009). Commercials advertising may promote the consumption of high-calorie and low-nutrient foods (Kumanyika et al., 2006).
The high prevalence of obesity among the lowest SES groups in developed countries does not seem to be homogenous within developing countries. It has been suggested that the burden of obesity spreads gradually and over decades from higher to lower
socioeconomic groups according to their ability to adopt healthy or unhealthy behaviours. According to Reddy (2007), at initial stages of the epidemiological and nutritional transition, the wealthier and more educated have higher incomes that make mediators of risk available to them, such as unhealthy foods and automated transport. In a posterior stage these mediators are available for the rest of the population
independently of their socioeconomic status; and in the last stage the population with better SES adopts healthy behaviours, health information and access more efficiently to health care.
This is supported by findings that suggest that the relationship between obesity and individual SES tends to be negative in countries with high levels of socioeconomic development; and positive in countries with medium and low levels of socioeconomic development (McLaren, 2007; Sobal et al., 1989). Moreover, the comparison of 37 developing countries showed that, in low-income countries, women who have low
education have lower prevalence of obesity than those with high education (Monteiro et al., 2004). However, in upper-middle income countries, women with low education have a higher prevalence of obesity than women with high education. These differences were noticeable when countries reached a GNP of US$2,500 per capita. Therefore, the association between obesity and SES may be determined by the socioeconomic
development of the country or region.
Obesity and socioeconomic status in Mexico
In Mexico, it has been suggested that obesity has a negative association with SES at the national level (Fernald, 2007; Rivera et al., 2004). However, a study found that the prevalence of obesity had an inverse u-shaped association with education; and a positive or inverse u-shaped association with household SES (Gomez et al., 2009). In addition, living in an urban area was associated with a higher risk of obesity.
Evidence from other studies suggests that the association between obesity and SES vary according to the level of urbanisation and sex. A study based on the NHS-2000 found that there is a negative association between obesity and SES (education and assets) among urban women (Buttenheim et al., 2010). In rural women, there was a non-linear association between obesity and SES. In urban men, there was a positive association between assets and obesity. And in rural men, there was a positive association between obesity and SES. A study in seven of the poorest communities of Mexico showed a positive association between BMI and SES (education, occupation, housing quality, household assets and subjective social status) both in men and women (Fernald, 2007).
The same study also found a positive association between BMI and household income but only in women. Therefore, there is not a clear pattern of association between obesity and SES in Mexico.