Time to put down that chocolate bar – what’s lurking in your food?

A new study shows that a diet rich in saturated fat results in depressive and anxiety behaviours.

Considering most of those “yummy” foods that a lot of us like, whether on the odd occasion or on an all-too-regular basis are high in saturated fat and sugar, a recent study from the University of Montreal Research Centre (CRCHUM) might entice us to put down that chocolate bar and pick up an apple instead.

We all know that a diet rich in saturated fat and sugar will ultimately lead to obesity and possibly diabetes, but did you know it causes inflammation in the brain as well? The researchers of the study claim that saturated fats create inflammation in the nucleus accumbens – the part of the brain associated with mood and reward – that leads to anxious, depressive and compulsive behaviours linked to metabolic dysfunction and obesity. It was published in the journal Molecular Metabolism providing more evidence on the harmful effects of too much-saturated fat on health.

“The depressive, anxiety and compulsive behaviours and the metabolic changes observed with the diet rich in saturated fat were not observed with a diet rich in monounsaturated fat, the type of fat found in olive oil,” says Stephanie Fulton, a CRCHUM researcher and professor in the Department of Nutrition of Université de Montréal’s Faculty of Medicine.

The metabolic impairments observed with the saturated high-fat diet include hyperinsulinemia and glucose intolerance, which are associated with the development of type II diabetes. Fulton and her team of researchers worked with two groups of mice fed a diet containing the same number of calories every day, 50 per cent of which were from fat. One of the groups was fed the saturated fat diet, while the other received monounsaturated fat, and the third group of mice was fed a low-fat diet.

“The animals with the diet rich in saturated fat voluntarily consumed more calories,” says Léa Décarie-Spain, the study’s first author and a PhD student in Fulton’s laboratory. “It took only 12 weeks for the diet rich in saturated fat to cause obesity, anxiodepressive behaviours and the metabolic changes associated with prediabetes.”

The Mediterranean diet has been and is currently praised for being rich in nutrients and low in saturated fats that alleviate and protect against negative thoughts patterns like depression. In this study, the researchers were able to identify neuronal mechanisms that give rise to depressive behaviour elicited by the diet-induced obesity. The study showed that anxiodepressive behaviours can result from inflammation observed in the nucleus accumbens. A genetic manipulation in that part of the brain made it possible to inhibit a molecule that plays a key role in advancing the inflammation.

“This manipulation succeeded in protecting the mice eating the diet rich in saturated fat from brain inflammation. Consequently, the signs of depression and anxiety and the compulsive sugar seeking disappeared,” explains Décarie-Spain. “Poor diet quality along with metabolic disturbances can lead to negative emotional states, which can stimulate the quest for comfort through food, and thereby lead to compulsive behaviour.”

These findings encourage further research into anti-inflammatory interventions that could inhibit depression caused by immune activity in the nucleus accumbens and really bring to the light the vicious power cycle that those who struggle with weight and obesity go through.

Saturated fat is typically seen in the form of palm oil – which is widely used in the processed food industry.

“We hope that this study will help educate people about the importance of diet, not only because of the link with cardiovascular diseases and certain cancers, but also because of the neurological and psychiatric problems that are increasingly associated with obesity,” says Fulton. “We also hope that our results will put pressure on the food industry to reduce saturated fat content in foods.”

Although a few sweet treats and a hamburger every now and then won’t bring on a case of depression, researchers still warn, “We should simply avoid eating such foods in excess in order to keep a healthy metabolism and inflammation at a minimum” said Décarie-Spain. “It’s a question of moderation.”

So maybe it’s time to put down that chocolate bar.

This study follows on an earlier study published by Fulton in 2013 which showed that obesity leads to anxiodepressive behaviours which have an impact on brain reward signaling and vulnerability to stress.  


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