Obesity changes brain chemistry: What new research means for healthcare

Obesity may permanently change the way the human brain reacts to food intake, according to new medical data, prompting some physicians and public health experts to call for insurers to cover medications for obesity.

Over 42% of American adults have been diagnosed with obesity, and nearly 31% of adults are medically overweight, according to the National Institutes of Health. Obesity has also been rising consistently in adults, children, and teenagers since 2000.


Obesity and nutrient sensing 

Research scientists and obesity medicine specialists from Yale School of Medicine found that medically obese participants experienced a nutrient-sensing deficiency even after having lost weight through diet and exercise.

The study, published in Nature Metabolism, specifically examined a region of the brain called the striatum, a portion of the basal ganglia that mediates the motivational aspects of food intake that regulate eating behavior. The researchers also monitored the level of dopamine, a neurotransmitter responsible for mood, pleasure, and pain regulation, in participants.

Participants were broken into two groups of “lean” and “obese” based on body-mass index, or BMI, and were fed via a feeding tube to bypass the oral pleasure of eating, focusing entirely on nutrient intake.

Lean study participants were found to have decreased striatal activity and increased dopamine levels when fed with both sugars and fats, leading to feelings of fullness, or satiation.

The striatal activity of obese participants, however, did not change in response to either sugars or fats, nor did dopamine levels increase in response to fat intake. These results indicate that patients with obesity have a reduced neurochemical capacity to process nutrient intake and experience sanitation. Participants with obesity who were able to lose 10% of their body weight in 12 weeks were then retested in the same manner, revealing no change in their brain chemistry relating to satiation.

“People still think obesity is caused by a lack of willpower,” Mireille Serlie, lead author and investigator in the study, told SciTech Daily. She explained, however, that the results have “shown that there is a real difference in the brain when it comes to nutrient sensing.

“This may be why people overeat despite the fact that they’ve consumed enough calories. And importantly, it might explain why it’s so hard to keep weight off,” Serlie said.

Possible public health response

Angela Fitch, president of the Obesity Medicine Association and a member of the board of directors of the Obesity Action Coalition, told the Washington Examiner that the results of the study are encouraging because they prove what clinicians have observed in the field.

“For years, we’ve been telling people that obesity is a disease … that has fundamental biological processes that are dysfunctional,” said Fitch.

Rather than solely treating obesity with diet and exercise, the results of the Nature Metabolism study indicate that the dysfunctional relationship between the gut and brain needs to be treated like other diseases rather than stigmatized as a personal failure.

“If you ask 10 people on the street ‘How do you treat breast cancer?’” said Fitch, “I guarantee there’s not going to be one person who says you can just will it away.”

Fitch recommends that anti-obesity medications, such as Wegovy and other semaglutide products, as well as surgical interventions, ought to be covered by medical insurance.

“Obesity as a disease state needs to be a standard benefit on all policies, including Medicare,” Fitch told the Washington Examiner.

Certain private companies and insurance plans have already begun covering anti-obesity medications. All federal employees have been covered for anti-obesity medications since this January.

Fitch sees that, with the cooperation of health insurance companies, drug manufacturers, and pharmacy benefit managers, it would be possible to increase access to care at a pace that matches the “huge demand” for anti-obesity medicine.

“Let’s just fix it,” said Fitch. “We have the power.”

Obstacles to addressing obesity

Determining who should be covered for obesity medicine care and how that care should function, however, could hinder implementing Fitch’s recommendations.

Changing standards of defining obesity may prove a challenge for health insurers assessing candidates for more comprehensive obesity medicine care.

The American Medical Association last week adopted a new policy advising against using BMI as a primary indicator for obesity because of its connection to “historical harm,” “racist exclusion,” and white norms of health.

Although BMI is a useful standardization that is easy to calculate, the measurement has also been criticized as not sufficiently distinguishing between fat and muscle weight, making it an imprecise tool.

A lack of patient willingness to stay on medications as prescribed could pose potential problems for insurance companies to cover weight loss and weight maintenance.

Jens Juul Holst, an endocrinologist at the University of Copenhagen who helped develop Wegovy and Ozempic, explained that people are unlikely to willingly stay on a semaglutide because of its appetite suppressant properties.

“What happens is that you lose your appetite and also the pleasure of eating,” Host said in an interview with Wired. “I don’t see that a huge part of the population will be put on Wegovy and will stay on Wegovy for the rest of their lives — I simply don’t see that picture,” added Holst.


Despite the challenges of addressing obesity in the future, the condition is a significant and growing strain on public health resources.

The World Obesity Federation in conjunction with the World Health Organization estimated that over half of the world’s population will be either overweight or obese by 2035. This could cost upwards of 3% of global GDP annually, which equates to the total spending on COVID-19 in 2020.

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