The stereotypes surrounding obese people usually center on one perception: that obese people must really enjoy their food. It is assumed that obesity provides such pleasure in food that all other interests are shuffled out of their lives. Hobbies are deserted and exercise is ignored, all for the sake of good food.
A new study challenges the misconception that obese people are critically overweight simply because they love to eat. The study, published in The Journal of Neuroscience shows that obese people may not love to eat at all. In fact, they may be overeating because eating is less pleasurable for them than it is for people not struggling with obesity.
The research focuses on the premise that obesity produces a vicious cycle in which the person overeats to compensate for reduced pleasure from food. The findings indicate that obese individuals have fewer pleasure receptors, and that they overeat to compensate.
The study was conducted at the University of Oregon brain imaging center by University of Texas at Austin senior research fellow and Oregon Research Institute senior scientist Eric Stice and colleagues. Stice explains that food intake is associated with dopamine release, with pleasure from eating coming from that release.
The findings of the study show that overeating may weaken the already depressed pleasure receptors, creating further diminishing of rewards from overeating. When a person has fewer dopamine receptors, they need to take in more of a rewarding substance to get the effect that other people would experience with less.
Stice explains that the findings explain why obesity is so resistance to treatment. The weakened reward increases the risk that a person will continue to gain weight in a “feed-forward” manner. Though there has been previous research that shows a weakened pleasure response in obese people, this study is the first to show that the overeating itself worsens the award circuitry.
The research team used Functional Magnetic Resonance Imaging (fMRI) to measure the levels of response to the participants’ taste of a chocolate milkshake. Control subjects consumed a tasteless solution. The researchers measured participants’ body mass index over a period of six months.
The results showed that the participants who gained weight had shown significantly less response to the milkshake at the follow-up relative to their baseline scan and relative to women who had not gained weight.
The findings of the study are significant, because while it has been understood that obese people lack a level of response to pleasurable stimuli, this is the first time that overeating has been shown to worsen the pleasure-response in the brain.