Eating junk food can cause fat to seep into the brain and trigger depression, according to a new study.
The research suggests that saturated fat actually enters the brain via the bloodstream.
Once there it affects the functioning of part of the brain that controls our emotions, the hypothalamus, and leads to an increase in depressive symptoms.
While the research was carried out in mice, scientists believe that the findings may explain the links between depression and obesity.
Anti-depressants are less effective on obese people than those of normal weight.
The researchers suggest that being obese is an additional factor causing depression, with the high fat diet to blame.
The study was led by the University of Glasgow and published in Translational Psychiatry.
The study looked at mice fed a diet of up to 60 per cent saturated and unsaturated fats and found parts of the fat – saturated fatty acids – were actually entering the brain via the bloodstream.
Researchers in this study believe that their novel findings may now influence new targets for antidepressant medications that may be more suitable for overweight and obese individuals.
Professor George Baillie, lead author of the study from the University of Glasgow, said: ‘This is the first time anyone has observed the direct effects a high fat diet can have on the signaling areas of the brain related to depression.
‘This research may begin to explain how and why obesity is linked with depression and how we can potentially better treat patients with these conditions.
‘We often use fatty food to comfort ourselves as it tastes really good, however in the long term, this is likely to affect one’s mood in a negative way.
‘Of course, if you are feeling low, then to make yourself feel better you might treat yourself to more fatty foods, which then would consolidate negative feelings.
‘We all know that a reduction in fatty food intake can lead to many health benefits, but our research suggests that it also promotes a happier disposition.
‘Further to that, understanding the types of fats, such as palmitic acid, which are likely to enter the brain and affect key regions and signaling will give people more information about how their diet can potentially affect their mental health.’