Brain Scans Reveal the Different Reasons Men and Women Gain Weight

Scientists have identified sex-specific brain signals associated with obesity which suggest that different drivers may lead to weight gain in men versus women.

“We found differences in several of the brain’s networks associated with early life adversity, mental health quality, and the way sensory stimulation is experienced,” study author Arpana Gupta, Ph.D., a brain, obesity, and microbiome researcher at UCLA, said in a statement.

“The resulting brain signatures, based on multimodal MRI imaging, may help us more precisely tailor obesity interventions based on an individual’s [biological] sex,” she said.

The study was published on April 6 in the journal Brain Communications.

The study included 78 men and women with a high body mass index (BMI) that put them in the overweight or obesity category and 105 men and women with a lower BMI.

BMI is a measure of body fat based on height and weight. A higher BMI does not always indicate higher body fat.

Participants filled out questionnaires assessing anxiety and depression symptoms, childhood trauma, sensitivity to common symptoms such as headaches and dizziness, food addiction, bowel symptoms, personality traits, and other factors.

They also underwent three MRIs to assess the structure and function of the brain, and the connectivity between different areas of the brain.

The results showed that specific changes in brain connectivity were associated with high BMI in both men and women.

This included “changes in many regions of the brain which respond to food or food-associated cues,” which were associated with early life trauma, researchers wrote.

They also found that women with high BMI showed changes in connectivity associated with greater anxiety and lower resilience, compared to what was seen in men with high BMI.

Other connectivity changes in women with high BMI suggest that women may have difficulty integrating emotions with action-directed goal planning, researchers wrote. This might lead to greater “emotional overeating” in women compared to men, they said.

In addition, certain brain changes suggest that women with high BMI may be more susceptible to the sight, smell, and taste of ultra-processed foods.

In an earlier study, Gupta and her colleagues found that emotion-related and compulsive eating appears to have a stronger influence on the development of obesity in women.

In contrast, men’s eating behavior tends to be affected more by awareness of gut sensations and visceral responses, such as those related to abdominal discomfort.

These results suggest that “in designing treatment plans for females with high BMI, it may be important to focus on emotional regulation techniques and vulnerability factors,” Gupta said in the release.

She and her colleagues caution that their research only shows associations between brain changes, BMI, and clinical markers such as anxiety and depression.

Additional research, including longitudinal studies, will be needed to determine whether brain changes lead to an increased BMI, or whether being overweight or having obesity shapes the brain in specific ways.

Dr. Mir Ali, a bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, Calif., said this study shows that weight loss is more complicated than what you eat and how much you exercise.

“Hormones, emotions, metabolism, genetics, and many other factors play a role,” Ali, who was not involved in the new study, told Healthline. In addition, “this study shows that there is a significant difference between men and women, in terms of emotions and eating.”

As for interventions for obesity such as a gastric sleeve or gastric bypass surgery, whether these are suitable for patients depends on factors other than their sex, such as BMI and other health conditions, said Ali.

In his experience, though, men tend to have higher success rates than women with surgical obesity interventions.

This may have to do with men’s eating behavior being shaped by gut sensations, as suggested by research by Gupta and her colleagues.

“Surgery primarily affects the visceral sensation,” said Ali, such as the feeling of fullness after eating.

“With people who are more emotional eaters, their body may be telling them that they are full, but their emotions are telling them to continue to eat,” he said, so surgery alone may not be as effective for them.

However, Ali said the experience of patients varies quite a bit, with some women doing very well after surgery for many years, while some men may gain weight shortly afterwards.

The results of the new study may have a bigger impact on other types of obesity interventions. Some research has already looked at the role of emotional regulation in weight loss, both in adolescents and older women.

However, the idea of customizing obesity interventions is not new. Physicians already do that with their patients, although they look at a number of factors, not just biological sex.

For example, “It is important to acknowledge each patient’s metabolic system and the social determinants of health,” said Dr. Ilan Shapiro, chief health correspondent and medical affairs officer at AltaMed Health Services in Los Angeles, who was not involved in the new study.

“When we address age, gender, mental health, and chronic diseases, it helps us to achieve the best interventional outcome,” he told Healthline.

Doctors also assess other factors, he said, such as the patient’s diet, patterns of exercise, sleep habits, stress level and management, and mental health.

In terms of sex-based obesity interventions, Shapiro said that currently there is no established method, but “hopefully, in the future, we’ll have more research to create an intervention template for patients.”

Another key factor that he thinks should be taken into account when designing obesity interventions is a person’s culture or community.

For example, community health workers — known in Spanish as promotoras or promotores — can help Hispanic communities practice healthy weight management, said Shapiro.

“As physicians, we aim to help patients build healthier and happier lifestyles,” he said. “So having culturally-competent physicians will help patients throughout their [weight-loss journey].”