According to the U.S. Centers for Disease Control and Prevention, over one-third of U.S. adults are obese.1 CDC defines obesity as a body mass index equal to or greater than 30. In simpler terms, a person 5 feet 4 inches tall is obese if she or he weighs 174 pounds or more; a person 5 feet 9 inches is obese if she or he weighs 203 pounds or more.
Obesity is related to some of the leading causes of death, including heart disease, some cancers, stroke, and type 2 diabetes. While obesity levels have been rising for all socioeconomic groups, some groups are more affected than others. Recent research highlights the complexity and variation in how socioeconomic status (SES) and obesity are related.
A study published in Social Science and Medicine used data for 67 countries representing all the regions of the world to examine how economic development, socioeconomic status, and obesity were related.2 The researchers used self-reported height and weight to calculate body mass index (weight relative to height), and looked at the relationship between obesity, gross national product, and SES (such as education, occupation, and income).
They found that obesity rose with a nation’s economic development, but also that socioeconomic status as it related to obesity changed. In lower-income countries, people with higher SES were more likely to be obese. Conversely, in high-income countries, those with higher SES were less likely to be obese. Why the reversal? It may be that in lower-income countries, higher SES leads to consuming high-calorie food and avoiding physically tough tasks. But in higher-income countries, individuals with higher SES may respond with healthy eating and regular exercise. The implication is that while economic development improves health, “problems of malnutrition are replaced by problems of overconsumption that differentially affect SES groups,” noted the authors. But some developing countries, such as India, are facing continued high levels of malnutrition along with a rise in obesity.3
What makes higher SES in high-income nations beneficial for staying thin? A study published in the Sociology of Health and Illness examined how weight and lifestyle were related, using data from 17 nations mostly in Europe.4 The researchers found that activities such as reading, attending cultural events, and going to the movies were associated just as much as exercise was with a lower BMI. On the other hand, people who participated in activities such as watching TV, attending sporting events, and shopping had higher BMI. These patterns were most consistent in high-income nations such as those in western Europe. In explaining how different sedentary activities could be associated with different weights, the authors suggested that the activities are “associated with body weight through a possible common cause—cultural tastes that in part distinguish SES-related group membership.”
Other researchers, in a study published in Demography, have also looked at how SES is related to obesity in the transition to early adulthood in the United States.5 They found a more nuanced relationship. For instance, men with a middle-class upbringing and lifestyle were almost as likely to be obese as those brought up in working-poor households but working now in lower-status jobs. For women, the relationships varied by race. For white females, all SES groups had a greater risk of obesity compared with the most advantaged. In contrast, among black women, only those from working-poor households who now had lower-status jobs were at increased obesity risk compared with the most advantaged group.
Overall, these studies show that factors that increase the risk of being obese affect SES groups differently, and may cause disparities in obesity between socioeconomic groups that worsen health and shorten longevity for those who are most disadvantaged.