25 September 2019

How do high-fat diets increase your appetite?

A new study has revealed that high-fat diets can cause neurological changes in the brain and cause you to eat more.

Most people are aware of the risks associated with high-fat diets such as problems with your heart health, obesity and compromising your immune system.

High-fat diets have also been linked to unfavourable changes in the type and number of gut bacteria – and now researchers are saying it can contribute to irregularities in the hypothalamus region of the brain, which is responsible for controlling body temperature, hunger, thirst, emotions, sleep, appetite and digestion. 

Malnutrition and obesity

The study, published in Cell Metabolism was conducted by researchers from Yale University and it looked at how a diet high in fat – specifically diets high in fats and carbohydrates – stimulates hypothalamic inflammation, which is a physical response to malnutrition and obesity.

This results in changes in the metabolism and causes you to eat more. The study was led by Sabrina Diano, the Richard Sackler Family Professor of Cellular & Molecular Physiology and professor of neuroscience and comparative medicine. 

Researchers found that inflammation occurs in the hypothalamus after three days of consumption of a high-fat diet. Diano, a member of the Yale Program in Integrative Cell Signaling and Neurobiology of Metabolism said: "We were intrigued by the fact that these are very fast changes that occur even before the body weight changes, and we wanted to understand the underlying cellular mechanism." 

Looking at inflammation of the hypothalamus in animals on a high-fat diet, the researchers found that changes were taking place in the physical structure of their microglial cells. Microglial cells act as the first line of defence in the central nervous system, regulating inflammation.

In order to see how diet affects the brain, researchers gave some rodents diets high in fats and carbohydrates, while others were given "regular" mouse food.

Inflammatory signal

Researchers found that the effect of the microglia springing into action was that neurons received an inflammatory signal, which lead to the mice eating more food. Eventually, the mice became obese. 

The study indicated that high-fat diets do not only affect people physically but it also emphasises that an unhealthy diet can alter food intake neurologically. "There are specific brain mechanisms that get activated when we expose ourselves to specific types of foods. This is a mechanism that may be important from an evolutionary point of view. However, when food rich in fat and carbs is constantly available it is detrimental."

Researchers would like to conduct more studies about the connection between the microglia and diseases of the brain, such as Alzheimer's disease. This neurological condition has been linked to changes in microglial cells, according to the National Institute of Health

Image credit: iStock


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