Why the Link Between Socio-Economic Status & Obesity?

Research has shown that there is a link between socio-economic status (SES) and obesity. People of lower SES are more likely to have a higher body mass index (BMI), while people of a higher SES are more likely to be leaner.  A recent study of more than 17,000 children in nearly 5000 neighborhoods found that kids in poor neighborhoods had a 28 percent greater risk of being obese compared to those in a wealthy neighborhood.  The study, from researchers at Rice University, found that obesity risk also was higher among children in neighborhoods with lower levels of education.

At the annual meeting of The Obesity Society, Leonard H Epstein, PhD, gave a talk about the possible influence of food reinforcement in this relationship between low SES and obesity. Food reinforcement value is defined as how hard a person is willing to work to obtain food, and is influenced by food palatability, food deprivation and food variety.  It’s known that people of low SES are more likely to experience food deprivation (which can lead to an increased perceived value of food).  Dr. Epstein’s studies found that people with higher income tend to find food less reinforcing. Epstein said his research has shown that food reinforcement is indeed a part of the low SES and obesity relationship.  “We can account for about 20 percent of the income/BMI relationship by taking into account a person’s food reinforcement value.” he said. “Food reinforcement mediates the relationship between education or income and obesity.”

Food reinforcement also seems to be associated with the ability to lose weight. In a 16 week study in children, Epstein found that the best weight loss was in kids who had low food reinforcement, and had lots of non-food alternatives provided to them. The next step is to take this understanding and try to build non-food reinforcements that are as powerful as food. Epstein added that it may be more difficult for low SES people to have as many alternatives for non-food reinforcements, since often those are associated with a cost.

Other research presented at the meeting focused on the relationship between food deprivation and obesity. John Kral, MD, spoke about data on food insecurity during pregnancy and the effect on offspring. 17.2 million US households faced “food insecurity” at some time during 2010. Food insecurity, Kral said, can be defined on a basic level as “has this person ever had to worry about whether he/she had enough food”.  In an animal study, Kral found that when offspring had elevated levels of CRF (a stress hormone), those elevated levels predicted adult obesity. A 12 week period of higher-stress in the moms during breastfeeding, was sufficient to create permanent problems in offspring including issues with glucose regulation. Offspring maintained these differences into adulthood.

Another presenter, Dr Jane Wardle, spoke about an example of this in history: a famine known as the Dutch Hunger Winter (1944-1945). Researchers found that the children of women pregnant during that winter had a 60 percent increased incidence of adult obesity, even though the famine was over and food levels were restored to a normal level by the time the children were born. Scientists believe the children had been programmed while they were still in the womb to think there was food scarcity, but when they were born it was into an environment with sufficient or abundant food. This difference in expected versus actual food environment is referred to as “mismatch”, is a potential explanation for elevated levels of obesity. These studies underline how food scarcity and the reinforcing value of food can impact one’s body weight, sometimes affecting us even before we are born.

Related Reading: Overweight Children a Product of Socioeconomic Status?

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