The finding came from new research on mice published by Dr. Stephanie Fulton, from the CRCHUM and the University of Montreal's Faculty of Medicine, in the International Journal of Obesity.
"By working with mice, whose brains are in many ways comparable to our own, we discovered that the neurochemistry of the animals who had been fed a high fat, sugary diet were different from those who had been fed a healthy diet.
The chemicals changed by the diet are associated with depression. A change of diet then causes withdrawal symptoms and a greater sensitivity to stressful situations, launching a vicious cycle of poor eating."
Over a six-week period, the team of experts fed one group of mice a low-fat diet, while feeding a second group of mice a high-fat diet, so that they could analyze how the different foods impacted the behavior of the animals.
Eleven percent of the calories in the low-fat diet consisted of fat, and 58% in the high-fat diet. This caused the high-fat group an 11% increase in their waist size, but they were not yet considered obese.
Fulton and her team then examined the association between rewarding mice with food and their behavioral and emotional outcomes by using a variety of methods that have been scientifically proven. The brains of the animals were also analyzed so that the experts could observe any changes that had occurred.
The researchers found that the high-fat group showed signs of anxiety, for example, they tried to avoid areas that were open. According to the authors, the animals' experiences physically changed their brains.
Dopamine was one of the molecules in the brain that was observed. It allows the brain to reward people with good feelings, which in turn, motivates individuals to acquire particular behaviors.
Dopamine is a chemical which works the same in humans as it does in mice and other animals. CREB is a molecule which regulates the activation of genes that play a part in the functioning of human brains, including the ones that cause dopamine to be produced. It also contributes to the forming of memories.
"CREB is much more activated in the brains of higher-fat diet mice and these mice also have higher levels of corticosterone, a hormone that is associated with stress. This explains both the depression and the negative behavior cycle.
It's interesting that these changes occur before obesity. These findings challenge our understanding of the relationship between diet, the body and the mind. It is food for thought about how we might support people psychologically as they strive to adopt healthy eating habits, regardless of their current corpulence."
The research is similar to a previous study which found that diets high in saturated fat and refined sugar can not only lead people to obesity, but also change their brains, making them want to eat more.
Written by Sarah Glynn