Overeating and the Brain?>

Overeating and the Brain

by UCB Health & Wellness Publications

If you often can’t resist the temptation to eat that second or may­be even third morning pastry, or find yourself frequently finishing off a whole pint of ice cream, you’re in good company. And the problem may not be your willpower.

A growing body of research suggests that the impulse to overeat is a complex phenomenon that’s profoundly affected by the actions of the nervous system. Scientists’ understanding of how the brain responds to food cues has come a long way, thanks in part to advances in brain scanning technology, genetic testing, and research on drug addiction and dependence.

This research may, in particular, help explain why some people just can’t seem to stick with the standard dietary weight-loss advice to consume fewer calories and cut back on unhealthy fats and highly processed carbs. Other studies are providing new strategies to help reduce appetite, bolster impulse resistance, and fight the urge to overindulge.

Your brain on food

It’s a common belief that people overeat because they lack willpower, but emerging evidence has shown similarities in the brain activity patterns of people who abuse alcohol and drugs and those whose overeating has an addictive quality. Still, whether or not there is such a thing as “food addiction” (a term used colloquially) is debated in the scientific community.

Many studies have looked at the relationship between the brain and overeating by scanning the brains of people when they are presented with a tempting food such as ice cream. In one study, in JAMA Psychiatry in 2011, 48 young women who had enrolled in a weight-loss program were categorized according to their level of “food addiction” as determined by their responses on a standard test. The participants were then presented with a chocolate milkshake while their brains were monitored via functional magnetic resonance imaging (fMRI). In the brain scans, the regions associated with both anticipation of reward and motivation to eat lit up more dramatically in the women with higher food addiction scores than in those with lower scores.

Investigators from the Oregon Re­search Institute have similarly been using brain imaging to examine activity in the dorsal striatum, a region of the brain that releases dopamine (which has been called the “pleasure chemical”) in re­­sponse to eating. In another milkshake study, which included 153 adolescents and was published in the Journal of Neuroscience in 2015, the researchers found, as ex­­pected, that the reward-related regions of the brain were activated when the beverage was presented.

More surprising, though, was the phenomenon of decreasing rewards. The teens who reported that they had eaten ice cream frequently during the previous two weeks showed less brain activation than those for whom this was a rarer pleasure. This suggests, the researchers said, that frequent consumption of a desired food may lead people to get less pleasure from it. The diminished response causes them to eat more to receive the same reward, leading to a cycle of overeating and weight gain. In other words, the brains of people who overeat crave more and more sugar and fat before reaching a feeling of satisfaction, or what scientists call the “pleasure threshold.”

Interestingly, a 2015 study in the Journal of Neuroscience suggested that the neurochemical reward pathways associated with obesity may have more in common with those involved in opioid addiction than with other addictions. Using positron emission tomography (PET) scans to compare the brain activity of 13 obese women with 14 nonobese women, Finnish re­­searchers found that the obese women had significantly lower availability of μ-opioid receptors (which are activated by opioids such as morphine) but no differences in the availability of dopamine receptors, which are associated more generally with addictive behavior.

A brain-based game plan

Though all of this is preliminary research and more studies are needed to turn what we know so far about the brain’s response to food into actionable advice, researchers have made considerable progress in looking into effective weight-loss strategies.

The traditional advice to eat smaller portions, count calories, and avoid sugary and high-fat foods is much harder to follow for some people. This suggests that for them, weight-reduction strategies that rely on willpower are almost certain to fail.

The good news is that the same body of research is suggesting new approaches to weight loss that may help reduce a person’s vulnerability to the cues involved in overeating and help bolster the ability to control reactions to food.

For example, in a study in the International Journal of Obesity in 2013, 21 adolescents were shown pictures of food they had previously rated as the most appetizing while their brains were monitored by fMRI. During the procedure, the participants employed three specific techniques used in cognitive behavioral therapy: First they thought about the long-term negative consequences of eating a desired food, then about the long-term benefits of not eating the food (potential weight loss, for example), and, finally, about not having cravings for the food.

Scans showed increased activation in numerous regions of the brain associated with impulse control during all three cognitive endeavors, with the most significant effect coming from thinking about the long-term positive gains from choosing not to eat the desired food. The conclusion: When faced with the temptation of a favorite treat, try imagining the long-term benefits that could come with setting it aside—not only weight loss but also im­­proved cholesterol, for instance, and other positive health outcomes.

Taming Food Temptations: 4 Strategies

These four tactics have shown promise in studies for reducing the impulse to overeat.

Similarly, researchers are looking into ways that the links between food addiction and obesity, specifically neurological chan­ges in the brain’s reward systems, might be harnessed for weight loss. For instance, the Finnish scientists whose research identified a deficit in opioid receptors associated with obesity suggest that the same treatment options being used for opioid addiction may also have potential applications in obesity treatment.

Neuroscientists are also exploring the use of electrical stimulation of deep brain structures and of the vagus nerve as possible treatments for obesity. These novel approaches are already being used for certain disorders, such as Parkinson’s disease and depression. This research is in its infancy, but a 2015 overview in the Annals of Neurosciences suggests it is promising.

Finally, scientists have gained a deeper understanding of the ways that tempting sugary and fatty treats trigger addiction-like neurochemical reactions. This is leading some experts to emphasize weight-loss strategies that focus on changing the food environment and reducing exposure to cues for sight, smell, and taste. The approach, outlined in a Drexel University study in the American Journal of Clinical Nutrition in 2018, involves removing all of one’s trigger foods from the home environment while also making lifestyle adjustments to avoid situations in which temptation is unavoidable. In other words, no more bake sales or all-you-can-eat buffets.

This article first appeared in the 2019 UC Berkeley Nutrition and Weight Control White Paper, medically reviewed by Christopher Gardner, PhD.

Also see Behavioral Therapy for Obesity.