The role of socio-cultural factors in the obesity epidemic

Obesity is socio-culturally distributed; that is the prevalence of obesity is known to vary according to socio-cultural factors, including socio-economic position, social roles and circumstance, and cultural factors. Further, these socio-cultural patterns are complex and specific to sex, age, and sometimes racial groups, as well as type of society, with patterns of relationships observed in developed countries sometimes reversed in developing countries. As described in Chapter 4, there is little doubt of the importance of the changing physical environment to the increases in obesity observed over the past several decades. However, far less attention has been paid to investigating the potential contribution of socio-cultural factors and to changes in the socio-cultural environment over time to the current obesity pandemic. The mechanisms through which socio-cultural factors may influence body weight and risk for obesity are also not well understood. In discussing socio-cultural influences we refer to systems of social relations (roles and relationships that define class, gender, ethnicity, and other social factors) and the meanings attached to these (1). For the purposes of this chapter, we focus on the impact of social, economic, and value systems on individuals' obesity-related behaviors (particularly, certain eating patterns and physical inactivity). In particular, we examine socio-cultural categories (socio-economic status, ethnicity, marital/family roles) for which evidence exists that rates of obesity are differentially distributed. We have not focused on the role of physical environmental factors, which is covered in Chapter 4, and we have largely restricted our focus to developed countries, from where the majority of the evidence for socio-cultural influences on obesity is derived. Issues relating to influences on obesity in developing countries are covered in detail in Chapter 5. This chapter provides an overview of the impact of socio-cultural influences on obesity in developed countries, and considers the potential pathways through which these influences may operate. The chapter concludes by speculating about the potential impact of societal trends on future rates and patterns of obesity in developed countries.

A comprehensive approach to obesity prevention

Part 1 Obesity 
Part 2 Biology of obesity
Part 3 Obesity and disease 
Part 4 Childhood obesity 
Part 5 Adult obesity 
Part 6 Management 
Part 7 Environmental and policy approaches
29 Obesity in Asian populations 431
30 Environmental and policy approaches: alternative methods 443
31 A comprehensive approach to obesity prevention 456

Genetic variation and obesity in Australian women: A prospective study.

Objective: A number of candidate genes have been implicated in the pathogenesis of obesity in humans. This study examines associations between longitudinal changes in body mass and composition and the presence of polymorphisms in the ß-3 adrenergic receptor, tumor necrosis factor-α, leptin, and leptin receptor (Lepr) in a cohort of Australian women.

Research Methods and Procedures: Healthy white Australian women (n = 335) were randomly selected from the Barwon region of Victoria and underwent baseline anthropometry and double-energy X-ray absorptiometry for assessment of body mass and adiposity. These measurements were repeated again at 2-year follow-up. Genomic DNA was extracted and used for polymerase chain reaction-based genotyping of all polymorphisms.

Results: The Pro1019Pro Lepr polymorphism was associated with longitudinal increases in body weight (p = 0.02), fat mass (p = 0.05), and body mass index (p = 0.01) in this study, and individuals homozygous for the A allele at this locus had a greater propensity to gain body fat over time. The largest effects on body composition seemed to be in individuals already obese at baseline. Changes in body weight, fat mass, percent body fat, and body mass index over a 2-year period were not associated with genetic variation in the ß-3 adrenergic receptor (Trp64Arg), tumor necrosis factor-α promoter, or leptin genes in non-obese or obese women.

Discussion: These results suggest that a Lepr polymorphism is involved in the regulation of body mass and adiposity in obese Australian white women, which may have implications for the treatment of obesity in this population.

Family food environments as determinants of preschool-aged children`s eating behaviours: implications for obesity prevention policy. A review.

Children's eating behaviours are fundamental to their health. Dietary surveys indicate that children's food consumption is likely to promote a range of diet-related diseases, including overweight and obesity, which are associated with a range of psychosocial and physical disorders. With the prevalence of overweight and obesity rapidly increasing, opportunities for informed prevention have become a focus of strategy. Diet is recognised as important in the genesis of obesity. We present data that demonstrate that eating behaviours are likely to be established early in life and may be maintained into adulthood. We review literature that shows that children's eating behaviours are influenced by the family food environment. These findings suggest that the family environment should be considered in developing obesity prevention strategy for children, yet the current strategy focuses primarily on the school environment. Those factors in the family environment that appear to be important include: parental food preferences and beliefs, children's food exposure; role modelling; media exposure; and child-parent interactions around food. However, the existing data are based on small scale and unrepresentative US samples. At a population level, we have few insights regarding family food environments and consequently little information about how such environments influence children's eating behaviours and thus their risk for obesity. We suggest research that may promote a better understanding of the role of family food environments as determinants of children's eating behaviour, and consider the implications for obesity prevention in Australia. (Aust J Nutr Diet 2001;58:19-25)

Behavioural determinants of the obesity epidemic

Obesity is a serious and growing public health problem affecting developed and developing countries. It is generally agreed that the causes of the current obesity epidemic are not genetic in origin, but are the result of changes in the environments in which we live. While acknowledging the importance of environmental factors, the central role of behaviour in the obesity epidemic cannot be ignored. It is our eating, physical activity and sedentary behaviours that form the interface between our biology and the environments to which we are exposed. However, a lack of understanding of the specific behaviours that are important in the aetiology of obesity poses a major constraint to preventing obesity. A better understanding of the behaviours that contribute to weight gain and obesity is critical in order to plan and implement effective obesity prevention initiatives.Theory-driven investigations of eating, physical activity and sedentary behaviours, their determinants, and their role in weight gain and obesity among different population groups are urgent research priorities. Without an understanding of the key behaviours that contribute to weight gain, and the influences on these behaviours, it will remain difficult to identify where to intervene in the environment and be confident that action will prevent obesity.

Which aspects of socioeconomic status are related to obesity among men and women?

OBJECTIVE: This study aimed to investigate the relationships between body weight and fat distribution, and four empirically derived domains of socioeconomic status: employment, housing, migration status and family unit.

DESIGN: A population-based study was used.

PARTICIPANTS: A total of 8667 randomly-selected adults (4167 men; 4500 women) who participated in the 1995 Australian National Health and Nutrition Surveys provided data on a range of health factors including objective height, weight and body fat distribution, and a range of sociodemographic indicators.

RESULTS: Results demonstrated associations for women, after controlling for age, between the employment domain, and body mass index and waist-to-hip ratio. Low status employed women were 1.4 times as likely to be overweight as high status employed women. There were less consistent relationships observed among these factors for men. Relationships between family unit and indicators of body weight and body fat distribution were observed for both men and women, with those who were married, particularly men (OR=1.6, 95% CI 1.4-2.0), at higher risk of overweight. The migration and housing socioeconomic status domains were not consistently associated with body mass index or waist-to-hip ratio.

CONCLUSIONS: These findings indicate that different components of socioeconomic status may be important in predicting obesity, and thus should be examined separately. Future research would benefit from investigating the underlying mechanisms governing the relationships between socioeconomic status domains further, particularly those related to employment and family unit and obesity

Elevated hypothalamic beacon gene expression in Psammomys obesus prone to develop obesity and type 2 diabetes

Objective: To investigate hypothalamic beacon gene expression at various developmental stages in genetically selected diabetes-resistant and diabetes-prone Psammomys obesus. In addition, effects of dietary energy composition on beacon gene expression were investigated in diabetes-prone P. obesus. Methods: Hypothalamic beacon gene expression was measured using TaqmanÔ fluorogenic PCR in 4-, 8- and 16-week-old animals from each genetically selected line. Results: Expression of beacon was elevated in the diabetes-prone compared with diabetes-resistant P. obesus at 4 weeks of age despite no difference in body weight between the groups. At 8 weeks of age, hypothalamic beacon gene expression was elevated in diabetes-prone animals fed a high-energy diet, and was correlated with serum insulin concentration. Conclusion: P. obesus with a genetic predisposition for the development of obesity and type 2 diabetes have elevated hypothalamic beacon gene expression at an early age. Overexpression of beacon may contribute to the development of obesity and insulin resistance in these animals.

New approaches to gene discovery with animal models of obesity and diabetes

DNA-based approaches to the discovery of genes contributing to the development of type 2 diabetes have not been very successful despite substantial investments of time and money. The multiple gene-gene and gene-environment interactions that influence the development of type 2 diabetes mean that DNA approaches are not the ideal tool for defining the etiology of this complex disease. Gene expression-based technologies may prove to be a more rewarding strategy to identify diabetes candidate genes. There are a number of RNA-based technologies available to identify genes that are differentially expressed in various tissues in type 2 diabetes. These include differential display polymerase chain reaction (ddPCR), suppression subtractive hybridization (SSH), and cDNA microarrays. The power of new technologies to detect differential gene expression is ideally suited to studies utilizing appropriate animal models of human disease. We have shown that the gene expression approach, in combination with an excellent animal model such as the Israeli sand rat (Psammomys obesus), can provide novel genes and pathways that may be important in the disease process and provide novel therapeutic approaches. This paper will describe a new gene discovery, beacon, a novel gene linked with energy intake. As the functional characterization of novel genes discovered in our laboratory using this approach continues, it is anticipated that we will soon be able to compile a definitive list of genes that are important in the development of obesity and type 2 diabetes.

An ecological study of the relationship between social and environmental determinants of obesity

There is growing concern with the increasing prevalence of obesity in industrialised countries, a trend that is more apparent in the poor than in the rich. In an ecological study, the relationship between an area measure of socioeconomic status (SES) and the density of fast-food outlets was examined as one possible explanation for the phenomenon. It was found that there was a dose-response between SES and the density of fast-food outlets, with people living in areas from the poorest SES category having 2.5 times the exposure to outlets than people in the wealthiest category. The findings are discussed.

Preventive strategies against weight gain and obesity

A well-resourced, comprehensive, population-based set of strategies is needed to
attenuate and eventually reverse the current trends of increasing obesity prevalence
now apparent in most countries. The Epidemiological Triad (host, vector,
environment) has proven to be a robust model for other epidemics and is applied
to obesity. Host-based strategies are primarily educational and these tend to
be most effective among people with higher incomes and higher educational
attainment. The main vectors for a high-energy intake are energy-dense foods and
drinks and large portion sizes and, for low energy expenditure, machines that
promote physical inactivity. Vector-based strategies that alter food formulation
can have a significant impact, particularly through influencing common, highvolume
foods. The increasingly ‘obesogenic’ environments are probably the main
driving forces for the obesity epidemic. There are many environmental strategies
that can influence the physical, economic, policy or socio-cultural environments,
but the evidence base for these potentially powerful interventions is small.
Children should be the priority population for interventions, and improving the
general socio-economic conditions for disadvantaged, marginalized or poor population
sectors is also a central strategy for obesity prevention. The key settings
for interventions are schools, homes, neighbourhoods, primary health care services
and communities. The key macroenvironments for interventions are the
transport and infrastructure sector, the media and the food sector.

Sustaining dietary changes for preventing obesity and diabetes: lessons learned from the successes of other epidemic control programs

A degree of success has been achieved in controlling several epidemics of infectious and non-infectious causes of death in countries, such as, Australia and New Zealand. Using the epidemiological triad (host, vector, environment) as a model, the key components of the control of these epidemics have been identified and compared to the current status of interventions to prevent obesity and its main disease consequence, type 2 diabetes. Reductions in mortality from tobacco, cardiovascular diseases, road crashes, cervical cancer and sudden infant death syndrome have been achieved by addressing all corners of the triad. Similarly, prevention programs have minimized the mortality from HIV AIDS and melanoma mortality rates are no longer rising. The main lessons learned from these prevention programs that could be applied to the obesity/diabetes epidemic are: taking a more comprehensive approach by increasing the environmental (mainly policy-based) initiatives; increasing the 'dose' of interventions through greater investment in programs; exploring opportunities to further influence the energy density of manufactured foods (one of the main vectors for increased energy intake); developing and communicating specific, action messages; and developing a stronger advocacy voice so that there is greater professional, public and political support for action. Successes in the other epidemics have been achieved in the face of substantial barriers within individuals, society, the private sector and government. The barriers for preventing obesity/diabetes are no less formidable, but the strategies for surmounting them have been well tested in other epidemics.