Could eating too much saturated fat affect your brain?

Eating too much saturated fat makes your brain struggle to control what you eat, according to new research by the University of Naples.

The study, which involved testing various diets on rats, has been published in the journal Frontiers in Cellular Neuroscience. The researchers found that saturated fat causes inflammation in the hypothalamus, an almond-sized part of the brain that regulates hunger.

The researchers observed reduced cognitive function in rats eating food rich in saturated fat, which made it more difficult for them to control their overall food intake.

Professor Marianna Crispino, the study’s lead author, said: ‘These days, great attention is dedicated to the influence of the diet on people’s wellbeing. Although the effects of high fat diet on metabolism have been widely studied, little is known about the effects on the brain.’

Crispino makes a distinction between saturated fat, such as that found in butter or fried food, and unsaturated fat, found in avocado or olive oil. The study found that unsaturated fat has no effect on brain function.

‘The difference was very clear and we were amazed to establish the impact of a fatty diet onto the brain. Our results suggest that being more aware about the type of fat consumed with the diet may reduce the risk of obesity and prevent several metabolic diseases.’

Instant analysis

This is a highly technical paper looking at a chemical in the brain responsible for the regulation of appetite, and how this interacts with the types of food we eat; namely those of a high fat diet. 

The aim of the paper is to find whether high fat diets affect appetite and the suppression of this, but also, whether inflammation is caused in the brain as a result, which explains the finding. 

The molecule looked at, AMPK, regulates food intake and by extension, other hormones also related to food intake like leptin, adiponectin, and insulin.  

The dietary regimen for the study involved three groups of rats: a control group, a fish oil diet, and a lard diet. Each of these rats were in a group of 8 and fed the diet for around 6 weeks. Over this time, body weights and food intakes were observed to track any changes. Another set of these animals were collected at 6 weeks, at 5 per group and injected with insulin. Blood was sampled at the end of the experiment to track changes in the hormone, glucose and lipid profile in the blood. 

Broadly, the effects observed were that the lard diet seemed to show a greater food intake in the rats while also increasing their body weights in addition. However, if you look at the control diet compared to the fat diets, you will notice that there is a discrepancy – the energy density of the control diet is actually lower than that of the lard diets. This makes me wonder whether the control diet is entirely appropriate to compare to, as it would have implications on absorption and perhaps metabolism – or at least opens up more questions as to the mechanism behind the results in the study. 

The lard diet tended to have an adverse effect on lipid metabolism and also the secretion of both insulin and Leptin, but not significantly so. However the basal amount of glucose produced in the diet with fish oil, was much greater compared to the control group. 

In the analysis of the hypothalamus after their rats had died, it was also noted that the pAMPK (phosphorylation AMPK) which is responsible for diet regulation and hunger suppression, was greatly increased compared to the other diets of control and fish oil. Interestingly when injected with insulin also, the rats consuming a lard diet did not change their pAMPK level after insulin injection either. 

The lard diet also showed a greater amount of oxidative stress and inflammation in the hypothalamus – something not shown in the fish oil group, where the levels of stress and inflammation were roughly similar to the controls, which also may have an implication in appetite control and dietary intake.

This however, is a theoretical study on a very small amount of rats – an animal model. While it does not translate to humans and only makes an inference, it is important to note that with small groups like this, it is important to increase the study numbers in order to make the science behind it more robust. However, provisionally, it looks as though a high lard diet may have an effect on appetite and hormonal control of appetite and lipid control that may cause a situation that the authors refer to as ‘hypothalamic dysregulation’ i.e. that chronic dietary changes to a high fat consumption can lead to altered hormonal function in the brain further compounding dietary function.

Research score 2/5