Changes in the way peoples’ brains are wired could explain some of the differences in obesity between men and women, new research published Thursday finds.
In women with obesity, changes in the brain tended to be centered on regions related to emotions, while in men with obesity, the changes tended to be found in regions that play a role in gut sensations, such as how hungry or full a person feels, the study found.
Past research has documented brain differences — such as changes in the structure and connectivity of the brain — in people who have obesity.
“This has implications for the way we view food, the way we crave it and how that leads to altered eating patterns and, in turn, obesity,” said Arpana Gupta, the director of the obesity program at the Goodman-Luskin Microbiome Center at UCLA, who led the study.
Gupta and her team wanted to dig in further to determine what role a person’s sex plays in neural pathways and how those pathways contribute to obesity in different ways.
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The study, published in the journal Brain Communications, confirmed that regardless of sex, differences in certain brain networks appear to be linked to being overweight or obese. But which parts of the brain those alterations affected appeared to be different in men and women.
While obesity in women appeared to be driven more by emotions and the reward of food, obesity in men appeared to be driven by the way they process feelings in the gut.
The study included 42 men and 63 women who, based on their body mass indexes, were not overweight or obese. They compared them to 23 men and 55 women who either were overweight or had obesity.
In addition to undergoing three MRI scans to assess brain structure, function and connectivity, the participants gave information about their behavior and mental health, including childhood trauma, bouts of anxiety and depression, food addiction and personality traits, as well as how sensitive they were to discomfort in their organs, such as indigestion, feeling full or feeling hungry.
The researchers compared all the data and found that in addition to the emotion-related brain changes’ being more common in women and the sensory-related changes’ being more common in men, some of the changes were also associated with childhood adversity and mental health issues.
Two key things influence how a brain is structured, said Bo Li, a professor of neuroscience at Cold Spring Harbor Laboratory in New York, who studies neurological drivers of obesity in mice.
“One is genetics. We inherit a lot from our parents, and that determines largely how our brains are structured. Another part is the influence of the environment,” Li said, adding that childhood and family experiences can change the brain’s wiring.
In the study, reports of childhood trauma and anxiety were higher among women with high BMIs compared to women who had lower BMIs and men. Those women were also more susceptible to emotion-driven and compulsive eating, being drawn to processed foods or having food addiction.
Especially during times of stress, “humans as a whole are evolutionarily trained to go after things that are immediate, intense and reliable,” said Warren Bickel, the director of the Center for Health Behaviors Research at Virginia Tech. “Food fits the bill, and processed food fits the bill even more.”
That is rooted in the fight-or-flight response, Bickel said. Repeated or prolonged stressful events during childhood wire the brain to be keenly aware of its immediate surroundings when adults feel stressed.
“It sets you up to be more trapped in the immediate environment, and the things you see in your immediate environment may have a bigger impact on you,” Bickel said, which means that if you see a food that is rewarding in the immediate future — say, a donut or an ad for fast food — you may be more prone to eating it on impulse if your brain is stuck in fight or flight.
Brain alterations associated with mood were more common in women, and things like anxiety and depression could also make a person less motivated to be active, another known driver of obesity.
The findings could have implications for personalized treatments for obesity, Gupta said, noting that the research also highlights the feedback loop between the brain and the gut.
“The brain patterns are part of the puzzle and show that the relationships with stress, environment, mood and early life experiences influence obesity and even that the gut has to be accounted for,” she said. “We have to take this whole-body approach when helping individual patients with weight loss.”
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