Western diets which are typically rich in fat and sugar promote excess calorie intake and weight gain; however, the underlying mechanisms are still unclear. Despite the knowledge of a well-documented association between obesity and altered brain dopamine function, it still remains elusive whether these alterations are:
1. Pre-existing, increasing the individual susceptibility to weight gain
2. Secondary to obesity
3. Directly attributable to repeated exposure to Western diet.
A study found that, eating food high in fat and sugar alters the brain’s reward centers to increase response to these foods and decrease the desire for low-fat and low-sugar foods. These brain adaptations may very well increase the risk of obesity.
Research studies at the Max Planck Institute for Metabolism Research in Cologne and the CECAD Cluster of Excellence for Aging Research at the University of Cologne in collaboration with Yale University, have now shown that foods which are very rich in sugar and fat change our brain.
The study was a randomized, controlled study involving fifty seven individuals who were not overweight. Researchers intended to look at the impact of food choices on the dopaminergic system, a pathway in brain that is involved in motivation and reward behavior.
The researchers offered one group of volunteers, in addition to their regular diet, a little pudding which had a lot of fat and sugar every day for a period of eight weeks to test this theory. The custard served to the opposing group had the same calories but a far less amount of fat. Brain activity was monitored in both groups before and after eight weeks.
Marc Tittgemeyer, who led the study, said, “The brain’s response to high-fat and high-sugar foods was greatly increased in the group that ate the high-sugar and high-fat pudding after eight weeks. This particularly activated the dopaminergic system, the region in the brain responsible for motivation and reward.”
“Our measurements of brain activity showed that the brain rewires itself through consuming chips and such foods. It subconsciously learns to prefer the rewarding food. Due to these changes in brain, we will unconsciously always prefer foods that contain a lot of fat and sugar.”
The test subjects did not acquire any additional weight than the test subjects in the control group during the study period, and their blood values, such as blood sugar or cholesterol, did not change either.
Participants who had eaten high-fat, high-sugar yogurt had a much less preference for low-fat foods than those who ate low-fat, low-sugar yogurt. The high-fat, high-sugar group also had increased brain responses when anticipating and consuming milkshakes.
According to the researchers, the preference for sweet foods is expected to show persistence even when the study will be over.
Marc Tittgemeyer said, “New connections are made in brain, and they don’t dissolve so quickly. After all, the whole point of learning is that once you learn something, you don’t forget it soon.”
“Our study demonstrates that short term daily consumption of high fat and sugar foods, reduces preference for a low-fat and low sugar food and rewires brain reward circuits to enhance response to palatable food. The surprising point was that the high fat and sugar food not only rewired brain circuits responding to food but also brain circuits critical for learning in general. Also, these effects occur without weight gain.”
This research indicates that exposure to an unhealthy food due to lack of access to healthy foods may alter the physiology, even in healthy-weight individuals, resulting in adaptations that tend to create a preference for unhealthy foods and promote overeating. This study clearly suggests that the food environment we live in has a profound impact on our eating patterns, rather than individuals being solely responsible for their food choices.
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