Table of Contents

Obesity, a condition affecting millions worldwide, has been linked to a myriad of health issues. However, recent studies reveal an alarming connection between obesity and the brain’s ability to recognise fullness, a crucial factor in weight management. This may suggest the high rate of weight regain that occurs after successfully losing weight.

The Connection Between Obesity and Brain Function

Obesity, defined by a Body Mass Index (BMI) over 30, has been found to impair the brain’s response to nutrients. In a controlled clinical trial, researchers fed sugar, carbohydrates, fats, or water directly into the stomachs of participants via feeding tubes. Using functional magnetic resonance imaging (fMRI) and single-photon emission computed tomography (SPECT), they measured the brain’s response to these nutrients.

In individuals with normal weight, brain signals in the striatum, a part of the brain involved in reward, slowed when food was consumed, indicating recognition of being fed. Additionally, dopamine levels rose, suggesting activation of reward centres in the brain.


Different Findings for Medically Obese

In medically obese individuals, brain activity did not slow down, and dopamine levels did not rise after consuming the same nutrients. 

People with obesity have significantly decreased brain reactions to nutrients after they have consumed them. It is important to note that the altered neural responses cannot be corrected even after diet-induced weight loss. Impaired neural responses to nutritional signals may contribute to overeating and obesity. Ongoing resistance to post-ingestive feeding signals after major weight reduction may help explain, at least in part, the high rate of weight regain that occurs after successful weight loss.

More concerning is that these brain changes associated with impaired fullness recognition may persist even after significant weight loss. A study found that a weight loss of 10% within three months did not reset the brain’s ability to recognize fullness in people with obesity. This could explain why people often regain weight due to irreversible brain changes that affect fullness recognition.

The Need for More Research

While these findings are significant, more research is needed to understand when brain changes occur during weight gain and what triggers them. Genetic factors may influence how the brain responds to nutrients and impact weight gain. The role of fat tissue, types of food consumed, and other environmental and genetic factors also need further investigation.

The Importance of Empathy in Addressing Obesity

Understanding the impact of a malfunctioning brain on food intake can increase empathy for those struggling with obesity. Weight stigma should be avoided as it oversimplifies the complex causes of weight gain.

Source: Nature