So THAT'S why slimming makes us depressed: Ditching fat and sugar is similar to drug withdrawal
Consuming a high-fat diet was linked with greater anxiety, say experts
This could make dieters vulnerable to a cycle of bingeing and fasting
12:39 GMT, 12 December 2012
12:46 GMT, 12 December 2012
The sight of a solitary carrot on your plate while your friends tuck into bags of crisps and chocolate is enough to make anyone feel glum.
But new research reveals that ditching a high-fat diet causes chemical changes in the brain that could make you vulnerable to a cycle of bingeing and fasting.
Scientists from the University of Montreal said their results suggested going on a diet could have a similar effect on the brain as drug withdrawal.
Tucking into fatty foods could make your brain more vulnerable to stress
Study leader Dr Stephanie Fulton said: '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 research team feed one group of mice a low-fat diet and a high fat diet to a second group over six weeks, monitoring how the different food affected the way the animals behave.
Fat represented 11 per cent of the calories in the low-fat diet and 58 per cent in the high-fat diet, causing the waist size in the latter group to increase by 11 per cent – not yet obese.
Next, the team used a variety of techniques to evaluate the relationship between rewarding mice with food and their resulting behaviour and emotions. They also 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 being anxious, such as an avoidance of open areas. Their brains were also physically altered by their experiences.
One of molecules in the brain that the researchers looked at is dopamine. It enables the brain to reward us with good feelings, thereby encouraging us to learn certain kinds of behaviour. This chemical is the same in humans as it is in mice and other animals. Certain genes involved in the production of dopamine are controlled by the CREB molecule.
'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 behaviour cycle,' Dr Fulton said.
'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.'