Going on a diet might feel similar to going through drug withdrawal, according to researchers at the University of Montreal’s Faculty of Medicine and its affiliated CRCHUM Hospital Research Centre. Eating fatty and sugary foods causes chemical changes in the brain, even before obesity hits. Ending the habit could lead to withdrawal symptoms and depression.

“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,” explains Stephanie Fulton, Ph.D., principal investigator. “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.”

The research team fed one group of mice a low-fat diet, and another group a high-fat diet, over the course of six weeks. The team monitored how the different food affected the way the animals behave. Fat represented 11% of the calories in the low-fat diet and 58% in the high-fat diet, causing the waist size in the latter group to increase by 11%—but they were not yet obese. Next, Dr. Fulton and her colleagues evaluated the relationship between rewarding mice with food and their resulting behavior and emotions. They also actually looked at the brains of the mice to see how they had changed.

Mice that had been fed the higher-fat diet exhibited signs of anhedonia, sensitivity to stressors, and being anxious, such as an avoidance of open areas. Moreover, their brains had been physically altered by their experiences. For example, CREB is a molecule that controls the activation of genes involved in brain function, including those that cause the production of dopamine. It contributes to memory formation. “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,” Dr. Fulton explains.

Withdrawal from the high-fat diet, but not the low-fat diet, potentiated anxiety and basal corticosterone levels and enhanced motivation for sucrose and high-fat food rewards.

“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 study is published in International Journal of Obesity with the title “Adaptations in brain reward circuitry underlie palatable food cravings and anxiety induced by high-fat diet withdrawal”.

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