If you’re feeling down or anxious without any apparent reason, there’s a chance those feelings may be linked to what you’re eating or more exactly, what you’re not eating. A study published this week in the International Journal of Obesity establishes a link to negative emotions, including depression and anxiety, with a high fat-high sugar diet.
Brain chemicals changed by a high fat diet
According to the results of this study, people who eat a lot of high fat junk food may actually be changing the brain’s chemistry. These changes lead to a cycle of eating that perpetuates the consumption of high-fat foods and often leads to obesity. In this study conducted by researchers at the University of Montreal, mice fed high fat and sugar diets displayed different chemical activity than the mice that were fed a healthy diet. When the group on the high fat diet were changed to healthy foods they more often showed signs of withdrawal. In these mice it was found that, “lasting changes in dopamine and plasticity-related signals in reward circuitry may promote negative emotional states, overeating and palatable food relapse.” In other words, the change in brain chemicals can lead to depression, anxiety, overeating, and the return to eating the high-fat, high-sugar foods.
“Anhedonia, anxiety and sensitivity to stressors develops during the course of HFD and may have a key role in a vicious cycle that perpetuates high-fat feeding and the development of obesity.” – International Journal of Obesity December 2012
To better understand what these results are saying, it helps to understand what “anhedonia” means. It’s the inability to experience pleasure from activities that are usually enjoyable.
How the study worked
While this study was conducted on mice, the results offer valuable insights. Researchers fed one group of mice a low-fat diet for 6 weeks (11 percent of calories from fat), while the other group were fed a high-fat diet for 6 weeks (58 percent of calories from fat). At the conclusion of the study, the mice who had eaten the high-fat diet showed significant weight gain and an 11% increase in waist size (in mouse terms), so they weren’t overweight enough to be considered obese, but when researchers analyzed their behaviors, emotions, and brains they found distinct differences between the two groups. The mice who had eaten the junk food diet displayed anxiety and had higher levels of the CREB molecule (plays a role in dopamine production) and higher levels of corticosterone (hormone associated with stress), and an ”enhanced motivation for sucrose and high-fat food rewards.”
While eating a high-fat diet for six weeks did not lead to obesity, the framework was laid. It left the mice with a longing for high fat and high sugar foods. According to the results of this study, the changes in brain chemicals created new feelings and behaviors that could lead to a vicious cycle of eating high-fat, high sugar foods, which would lead to overweight or obesity and a struggle with depression.