A new study from the University of Alberta challenges the notion that advertising junk food is at the root of the obesity epidemic.
Growing up in a low social-economic environment is more of a precursor to obesity later in life than junk food advertising, according to the report, with adults who grew up in a stressful childhood environment more likely to crave food even when they are not hungry.
Jim Swaffield
The study was conducted by Jim Swaffield, consumer psychology researcher with the Alberta School of Business and Qi Guo, a researcher from the Faculty of Education.
Swaffield explains it has long been known that stress triggers appetite: “However, what we did not know was that stressful conditions experienced during early childhood appear to calibrate the brain to desire high-energy-dense foods throughout one’s lifespan. This research also helps explain why people with lower socio-economic status, who live in chronically stressful conditions, have higher obesity rates.”
For the study, 311 adults (133 men and 178 women) were shown random images of food items from each of the six major food categories – vegetables, fruits, grains, dairy, meat/poultry, and sweets – and rated how desirable each food item is.
Participants rated each food on a seven-point scale according to the question, “How desirable is this food item to you right now?” with seven being extremely desirable.
The food items were split into two equally sized groups based on caloric content. Foods that contained fewer than 1.49 calories per gram were classified as low-energy-dense foods, and foods with more than 1.5 calories per gram were classified as high-energy-dense foods.
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The participants were then asked a series of questions about their early childhood socio-economic conditions and current stress level.
Next, Swaffield and Guo administered a questionnaire to determine whether the participants had a state or trait appetite. State appetite refers to the desire to eat only when one is hungry due to low glucose levels; trait appetite refers to those who desire food even when they are not hungry.
They discovered that adults raised in harsh socio-economic conditions were very food motivated and more likely to have trait appetite. In contrast, adults raised in safe socio-economic conditions were more likely to have a state appetite.
Moreover, adult participants who lived in a high socio-economic environment during childhood were likelier to desire low-energy-dense foods. In contrast, adults raised in a low socio-economic environment during childhood had a low desire for low-energy-dense foods.
Swaffield says the dominant theories as to why stress triggers the desire to eat include the insurance hypothesis, which postulates that humans have an instinctive drive to overeat to acquire excess fat stores that would buffer the impact of a future famine.
“It is believed that as environmental conditions become harsh, a sense of resource scarcity is felt, which creates a sense of stress,” he says. “To reduce stress, humans are driven to acquire and consume excess food. This is a pattern that has also been found in birds, rodents and non-human primates.”
Another belief as to why stress can increase the desire for high-energy-dense foods is that stress signals to the body that it needs to prepare for a fight-or-flight response.
“Fighting or fleeing is how one reduces the cause of the stress. To fuel this response, our muscles need to mobilize stored glucose and fats as quickly as possible.”
Swaffield adds that stress increases the desire for high-energy-dense foods because energy-dense foods trigger production of the neurotransmitter dopamine, which blunts the stress response and makes the person feel better.
Swaffield and Guo’s study comes as pressure mounts to ban the advertising of junk food. And though banning junk food ads makes intuitive sense, Swaffield notes there are real-world implications if the correlation between obesity and advertising is spurious.
“If we err in identifying the cause of obesity, we will fail to develop a strategy to remedy this problem, and the number of people who live with these conditions will continue to grow.”
| By Michael Brown
Michael is a reporter with the University of Alberta’s Folio online magazine. The University of Alberta is a Troy Media Editorial Content Provider Partner.
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