High-Fat Diet May Cause Anxiety And Depression

22 Oct 2015 --- A new study in mice reveals that increased body weight and high blood sugar as a result of consuming a high-fat diet may cause anxiety and depressive symptoms and measurable changes in the brain.

Dr. Bruno Guiard, senior author of the British Journal of Pharmacology study said, “The link between type 2 diabetes mellitus and depression is bidirectional. However, the possibility that metabolic disorders may cause anxiogenic/depressive-like symptoms or alter the efficacy of antidepressant drugs remains poorly documented. This study explored the influence of type 2 diabetes on emotionality and proposed a therapeutic strategy that might be used in depressed diabetic patients.”

Mice were fed a high-fat diet and subjected to metabolic and behavioral analyses to assess a link between metabolic and psychiatric disorders. Researchers then looked at whether administration of a selective serotonin reuptake inhibitor (SSRI) or high-fat diet withdrawal could reverse the dietary-induced metabolic and behavioral changes.

The beneficial effects of an antidepressant were also blunted in mice fed a high-fat diet. "When treating depression, in general there is no predictor of treatment resistance," said Dr. Bruno Guiard, senior author of the British Journal of Pharmacology study. "So if we consider metabolic disorders as a putative treatment resistance predictor, this should encourage psychiatrists to put in place a personalized treatment with antidepressant drugs that do not further destabilize metabolism."

On the other hand, taking mice off a high-fat diet completely reversed the animals' metabolic impairments and lessened their anxious symptoms. "This finding reinforcing the idea that the normalization of metabolic parameters may give a better chance of achieving remission, particularly in depressed patients with type 2 diabetes," said Dr. Guiard.

“Our data show that increased body weight, hyperglycemia and impaired glucose tolerance in response to a high fat diet are correlated with anxiogenic/depressive-like symptoms. Interestingly, we also found that the beneficial effect of prolonged administration of SSRI was completely blunted in high-fat diet fed mice. On the contrary, dietary withdrawal completely reversed metabolic impairments and positively impacted anxious symptoms, although some behavioral anomalies persisted.

It is unclear what kind of fats the mice were fed, although the standard chow used in trials tends to consist of saturated fats. It is important to differentiate between various fatty acids and their effects on brain health, as it is well documented that some fatty acids such as polyunsaturated like omega 3 and monounsaturated fats from olive oil and avocados in fact are beneficial for brain health and depression, reducing the need for SSRI’s.

Trials such as this may confuse the public unless the type of fat is specified, leading them down the “all fats are harmful” path that was popular in the 1970’s and 1980’s and which we now know to be misleading.

The results set the tone for future investigations on potential mechanisms that may link metabolic and psychiatric disorders.