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Food Choices And Brain Structure Influence Becoming Overweight

by — 2016-07-23 in Weight Loss
Overweight people tend to choose unhealthier foods to eat compared to lean people, even though both groups seem to make similar choices when given hypothetical situations. Brain activity seems to be a good predictor of which foods finally get chosen.

Being overweight or obese increases a person's morbidity and mortality risk worldwide as they are associated with the development of issues such as cardiovascular diseases, type 2 diabetes and certain cancers.

Research was conducted by the University of Cambridge in the U.K. to look what food choices were made by overweight people and what factors made them decide on such choices. 

It was noted that although overweight and lean people made similar hypothetical food choices when questioned by researchers, it was observed that overweight people made unhealthier choices when picking out real food to consume. It was then discovered that there were structural differences in key areas of the brain involved in processing value judgements in overweight/obese people. 

Findings of the study

Researchers interviewed 40 overweight and 23 lean individuals to rate pictures of 50 commonly available snacks regarding the healthiness and tastiness of the products. The participants were then examined to see whether they had an inclination to replace their choices with a certain product that was marked as being neutral.

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A neutral product would be shown to the participants at the beginning of the task. The task then was to compare the neutral product with the given one, and the participant had to decide whether they would replace the neutral product or keep it as is. This was all done while the participants were placed in a functional magnetic resonance imaging (f-MRI) machine and had their brain activity interpreted.

It was found that the willingness to swap a given food was associated with increased activity in the ventromedial prefrontal cortex of the brain; an area which is known to be linked with the degree in which people value rewards. The activity in this area was similar across both groups in the above-mentioned task. In another study it was noted that the grey matter, of the mentioned area of the brain, in people with a higher body mass index seemed to be thinner

Following this test, the participants were invited to enjoy an all-you-can eat-buffet. This spread included healthy and not-so-healthy food choices. The buffet choices were then rated on a scale of healthiness and tastiness, just like in the visual test. 

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It was noted that brain activity predicted the proportion of healthy food that would be consumed by people from both groups based on the tastiness of those foods. What was also discovered was that the participants in the overweight group tended to consume more unhealthy foods than their lean counterparts.

Another aspect that was measured in this study was the impulsivity or self-control of the participants. It was noted that individuals in the overweight group seemed to have higher levels of impulsivity which had a direct effect on their unhealthy food choices. This was true when choosing real foods to eat and not so in the visual test.

The clinical significance of this study

Clearly, there's a big difference when overweight people are making hypothetical and real food choices. It would seem then that food choices don't appear to be based on a rational decision, and these findings would suggest that just trying to educate people about the healthiness of food choices is just not enough.

The problem of translating what one decides hypothetically versus what decisions are made in the real world could lie in the structural differences in the brain or overweight people.

The Ventromedial Prefrontal Cortex And Obesity 

Anatomy

The ventromedial prefrontal cortex (vmPFC) is an area of the brain which is located in the frontal lobe at the bottom of both cerebral hemispheres. The function of the vmPFC is to adequately regulate emotional responses and to make aid in making morally acceptable decisions.

Injury or damage

Injury or damage to the vmPFC may result in certain issues and they include the following:

Emotional regulation 

  • Damage to the vmPFC in early childhood may result in patients with severe antisocial behaviour as well as making impaired moral judgements.
  • Emotions which can't be controlled may result in the patient committing crimes due to the inhibition factor that's missing.
  • Emotional responsiveness in decreased and they show less emotions.
  • In certain situations, patients may exhibit poorly regulated frustration and anger.
  • Personality changes such as lack of empathy, poor decision making and irresponsibility can occur.

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Gender specific social cues

  • There's an inability for these patients to process gender-specific social cues and thus showed impaired stereotypical social knowledge.

Decision making

  • Lesions in the vmPFC may lead to impaired social and personal decision making abilities. Here, there's difficulty in deciding between options which have uncertain outcomes, regardless of what the uncertainty is.
  • These patients also find it difficult to learn from their mistakes, and they may end up repeating the same wrong decision over and over again. 
  • The involved individual may choose to make decisions which result in an immediate reward, despite the consequences of their actions.
  • Damage to the vmPFC, in the right hemisphere of the cerebrum, may result in an inability to detect sarcasm, deception and irony.
  • Injury to the left vmPFC can affect primitive defense mechanisms such as verbal denial, fantasy, splitting and projection. Injury to the right vmPFC can affect mature defense mechanisms such as compensation, intellectualization, isolation and reaction formation.
  • Moral judgements seem to be made only in hypothetical situations, and therefore their decisions made in a real-world setup seem to be inconsistent with their moral beliefs. There seems to be a misinterpretation in reasoning when applying the same moral principles to situations in their lives.

Cocaine use

  • The use of cocaine has been associated with decreased function of the vmPFC. When users were asked to perform tasks which required activation of the vmPFC, they would perform poorly.

  • Chronic use of cocaine has been shown to result in a decrease of the grey matter in the vmPFC. The pyramidal cells in this area of the brain are also linked to drug/reward seeking behaviour.

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Disruption in addiction

Dysfunction of the vmPFC has been shown to be associated with addiction. In certain situations, activation of the injured vmPFC may result in a patient to exhibit or relapse into addictive behaviours. 

Increased physical or emotional stressors in these patients may result in the inability to suppress their emotional intensity, such as having a negative mood affect or becoming anxious. This can then result in enhanced motivation to seek out and Procure drugs, alcohol or other addictive substances or behaviours. Motivation for other goals are non-existent. 

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