The Gut-Brain Connection: Possible Reason For Your Fatty-Food Cravings

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Craving fatty foods is very normal. With its great taste, pleasing texture, and aroma, fatty foods such as burgers, donuts, or pizzas can be very hard to resist. Our bodies have been hardwired to prefer rich, high-calorie foods because they’ll give you more energy for longer. 

There are several suggested reasons behind our fatty food cravings. Some say that it can be linked to nutritional deficiency since fats are essential to a healthy diet necessary for certain bodily functions. Hence, fat cravings may be an attempt for your body to get nutrition. Others suggest that fat cravings may be rooted in psychological reasons, as most people choose fatty foods as comfort foods when they are bored, stressed, or upset.

In addition, new research from Columbia’s Zuckerman Institute that examined the source of our appetites has discovered an entirely new association between the gut and the brain that drives our desire for fat. 

Discovering The Gut-Brain Connection Driving Cravings For Fat

Obesity is one of the most prevalent global health concerns affecting millions today. According to the World Health Organization, the majority of the world’s population live in countries where overweight and obesity causes more death than underweight.

WHO also identified an energy imbalance between calories consumed and calories expended as one of the primary causes of obesity and overweight. The prevalence of physical inactivity and intake of energy-dense foods high in fat and sugars also largely contribute to obesity and overweight, elevating the risks of certain health conditions like heart disease and stroke.

Hence, improved knowledge of the gut-to-brain mechanism that drives more fat consumption can significantly help form interventions to treat obesity and other associated health conditions.

A recent study from Columbia’s Zuckerman Institute published in the journal Nature pondered on this. It explored the neural basis for fat preference and identified receptors and neuronal elements mediating its development.

They identified the vagal neurons responding to intestinal fat delivery using single-cell data. The researchers then proceeded to record the activity of vagal neurons by alternating gut stimulation with fat and sugar to examine how vagal neurons respond to these two nutrient signals in the gut. They were able to evaluate over 1800 vagal sensory neurons from 22 nodoses. The researchers also performed a series of mice experiments for a comparative analysis of the gut-to-brain pathways enabling preference for fat vs. sugar. 

Based on their analysis, the researchers discovered that:

“The gut tells our brain what we want, what we need.” – Charles S. Zuker, HHMI Investigator at Columbia University

  • Glucose activates a particular gut-brain circuit which communicates to the brain in the presence of intestinal sugar.
  • Calorie-free artificial sweeteners are found to have no similar effect on the brain, possibly explaining why diet sodas can leave us feeling unsatisfied.
  • Unlike artificial sweeteners that send signals to the brain only after tasting but not after swallowing, fat keeps the brain alert post-ingestion even after reaching the gut, which drives our cravings.

Based on these findings, the researchers assumed that fat must be activating specific parts of the brain driving the animals’ behavioral response to fat. To confirm this, they conducted further experiments using mice and found that neurons in the vagus nerve, linking the gut to the brain, perked up when mice had fat in their intestines.

Taking a closer look at the gut itself, particularly the endothelial cells lining the intestines, the researchers found two groups of cells that sent signals to the vagal neurons in response to fat:

  • One group of cells that functions as a general sensor of essential nutrients which respond not only to fat but also to sugars and amino acids
  • Another group responds only to fat, potentially helping the brain recognize fats from other substances in the gut.

To fully confirm these findings, the researchers went further by blocking the activity of these cells using a drug and utilizing genetic techniques to deactivate either the vagal neurons themselves or the neurons in the cNST. In both cases, a mouse lost its appetite for fat.

This study clearly demonstrated a gut-to-brain circuit that facilitates preference for fat. Furthermore, the researchers showed that fat, like sugar, uses the gut-brain axis to drive consumption.

This finding is crucial in creating interventions that will help address the increasing prevalence of obesity which results in other adverse health outcomes and the development of various conditions such as diabetes, heart disease, and stroke. Further research on this new-found relationship may also eventually lead to treatments that may help address obesity by minimizing an individual’s high-calorie fatty foods’ excessive cravings.

Journal Reference

Li, M., Tan, H.-E., Lu, Z., Tsang, K. S., Chung, A. J., & Zuker, C. S. (2022). Gut-brain circuits for Fat Preference. Nature. https://doi.org/10.1038/s41586-022-05266-z 

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