If a study on rats can be extrapolated to humans, giving up junk food can cause symptoms similar to drug withdrawal.
In the University of Montreal study, rats were feed a high-fat, sugary diet for six weeks. Afterwards, given healthier food, they became more anxious and depressed.
The Live Science website explained what the scientists found:
“The researchers then examined the brains of the mice and discovered significant changes had occurred: Mice on the high-fat diet had increased levels of corticosterone — a hormone associated with stress — and CREB, a protein closely linked to dopamine functioning. Dopamine is a neurotransmitter that causes feelings of reward, and is activated by (among other things) addictive drugs like cocaine and methamphetamine.”
In a statement, study co-author Dr. Stephanie Fulton summarized the findings as follows:
“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.”
The study, published in the International Journal of Obesity, concluded that “anhedonia, anxiety and sensitivity to stressors develops during the course of [high-fat diet] and may have a key role in a vicious cycle that perpetuates high-fat feeding and the development of obesity.”