Social determinants of obesity
While genetic influences are important to understanding obesity, they cannot explain the current dramatic increase seen within specific countries or globally. It is accepted that calorie consumption in excess of calorie expenditure leads to obesity, however what has caused shifts in these two factors on a global scale is much debated.
Changing rates of obesity are related to a number of social phenomena including: social class, smoking status, number of children people have, and urbanization.
See Also : Social determinants of health in poverty
The correlation between social class and BMI varies globally. A review in 1989 found that in developed countries women of a high social class were less likely to be obese. No significant differences were seen among men of different social classes. In the developing world, women, men, and children from high social classes had greater rates of obesity. An update of this review carried out in 2007 found the same relationships, but they were weaker. The decrease in strength of correlation was felt to be due to the effects of globalization.
Many explanations have been put forth for associations between BMI and social class. It is thought that in developed countries, the wealthy are able to afford more nutritious food, they are under greater social pressure to remain slim, and have more opportunities along with greater expectations for physical fitness. In undeveloped countries the ability to afford food, high energy expenditure with physical labor, and cultural values favoring a larger body size are believed to contribute to the observed patterns. Attitudes toward body mass held by people in one's life may also play a role in obesity. A correlation in BMI changes over time has been found between friends, siblings, and spouses.
Those who quit smoking gain an average of 4.4 kilograms (9.7 lb) for men and 5.0 kilograms (11.0 lb) for women over ten years. Changing rates of smoking however have had little effect on the overall rates of obesity.
Malnutrition in early life is believed to play a role in the rising rates of obesity in the developing world. Endocrine changes that occur during periods of malnutrition may promote the storage of fat once more calories become available.
Number of children
In the United States the number of children a person has had is related to their risk of obesity. A woman's risk of obesity increases by 7% per child, while a man's risk increases by 4% per child. This could be partly explained by the fact that having dependent children decreases physical activity in Western parents.
In the developing world urbanization is playing a role in increasing rate of obesity. In China, overall rates of obesity are below 5%. However, in some cities, rates of obesity are greater than 20%.
- Yach D, Stuckler D, Brownell KD (January 2006). "Epidemiologic and economic consequences of the global epidemics of obesity and diabetes". Nat. Med. 12 (1): 62–6. doi:10.1038/nm0106-62. PMID 16397571.
- Sobal J, Stunkard AJ (March 1989). "Socioeconomic status and obesity: A review of the literature". Psychol Bull 105 (2): 260–75. doi:10.1037/0033-2909.105.2.260. PMID 2648443.
- McLaren L (2007). "Socioeconomic status and obesity". Epidemiol Rev 29: 29–48. doi:10.1093/epirev/mxm001. PMID 17478442.
- Christakis NA, Fowler JH (2007). "The Spread of Obesity in a Large Social Network over 32 Years". New England Journal of Medicine 357 (4): 370–379. doi:10.1056/NEJMsa066082. PMID 17652652.
- Flegal KM, Troiano RP, Pamuk ER, Kuczmarski RJ, Campbell SM (November 1995). "The influence of smoking cessation on the prevalence of overweight in the United States". N. Engl. J. Med. 333 (18): 1165–70. doi:10.1056/NEJM199511023331801. PMID 7565970.
- Chiolero A, Faeh D, Paccaud F, Cornuz J (1 April 2008). "Consequences of smoking for body weight, body fat distribution, and insulin resistance". Am. J. Clin. Nutr. 87 (4): 801–9. PMID 18400700.
- Caballero B (March 2001). "Introduction. Symposium: Obesity in developing countries: biological and ecological factors". J. Nutr. 131 (3): 866S–870S. PMID 11238776.
- Weng HH, Bastian LA, Taylor DH, Moser BK, Ostbye T (2004). "Number of children associated with obesity in middle-aged women and men: results from the health and retirement study". J Womens Health (Larchmt) 13 (1): 85–91. doi:10.1089/154099904322836492. PMID 15006281.
- Bellows-Riecken KH, Rhodes RE (February 2008). "A birth of inactivity? A review of physical activity and parenthood". Prev Med 46 (2): 99–110. doi:10.1016/j.ypmed.2007.08.003. PMID 17919713.
- "Obesity and Overweight" (PDF). World Health Organization. Retrieved February 22, 2009.