Field Notes

Differences in Brain Activity Found in Obese Men vs Women

A new study of obese people suggests that changes in their brains’ reward regions make them more prone to overeating, and that women and men exhibit different brain activity related to overeating.

Researchers from UCLA found that women who are obese showed more prominent changes in the reward system related to dopamine responsiveness, suggesting that emotion-related and compulsive eating play a larger role in their overeating. Men who are obese showed a different pattern of brain remodeling in sensorimotor regions, a sign that their eating behavior is affected by a greater awareness of gut sensations and visceral responses.

Stress and drug use are known to affect how sex and sex hormones modulate the function of the mesolimbic dopamine system, which is involved in brain’s reward system. It’s possible that these factors lead to reduced dopamine signaling, according to research. Past studies also have demonstrated how altered processing of rewarding stimuli results in excessive eating. These new findings show that obesity has similar types of effects on the mesolimbic dopamine system.

The researchers collected brain images from 124 individuals (61 males and 63 females) who didn’t have significant medical or psychiatric conditions. They then calculated how the brain’s reward, sensorimotor, and salience—the brain’s way of making appropriate responses based on biological and cognitive stimuli—networks are related to information flow. The individuals were divided into four groups based on their BMI and sex: males with high BMI, males with normal BMI, females with high BMI, and females with normal BMI.

A person’s sex hasn’t been sufficiently considered as a factor when it comes to devising a treatment plan for obesity, according to the study’s authors. This research is the first to examine sex-related differences in characterizing the prominence and signaling of brain regions in obesity. A better understanding of sex differences in obesity may enable medical professionals to more precisely tailor individual treatments.

— Source: UCLA Health Sciences


Healthful Lifestyle May Reduce Colon Cancer Recurrence Risk

Colon cancer patients who have a healthy body weight, exercise regularly, and eat a diet high in whole grains, fruits, and vegetables have a significantly lower risk of cancer recurrence or death, according to a research team led by University of California, San Francisco (UCSF) investigators. This finding represents an analysis of data collected on patients participating in a national study for people with stage III colon cancer. The analysis involved 13 other institutions, and patients were evaluated over approximately seven years.

“We found that colon cancer patients who reported a healthy body weight, engaged in regular physical activity, and ate a diet rich in whole grains, vegetables, and fruits that was low in red and processed meats had a lower risk of cancer recurrence and death compared with patients who did not engage in these behaviors,” says lead author Erin L. Van Blarigan, ScD, an assistant professor in the UCSF departments of epidemiology and biostatistics, and urology.

The new findings from this federally funded clinical study provide scientific evidence that cancer survivors may improve their outcome if they follow healthful lifestyle guidelines. This was a prospective study among nearly 1,000 stage III colon cancer patients enrolled in a chemotherapy trial conducted across the United States from 1999–2001. Clinical researchers from Harvard administered a validated questionnaire on lifestyle at two points during the trial. These data were made available to a team led by UCSF researchers, who performed the analysis. Patients were given a score from 0 to 6 measuring the degree to which their lifestyle matched the American Cancer Society Nutrition and Physical Activity Guidelines for Cancer Survivors. Only 9% of the patients in the study had a lifestyle that adhered closely to the healthy lifestyle guidelines, indicated by a score of 5 or 6. Researchers found that over a median follow-up period of seven years, colon cancer survivors who adhered to the healthy lifestyle guidelines had a 42% lower risk of death and 31% lower risk of cancer recurrence compared with patients who didn’t engage in these behaviors. There were 335 people with colon cancer recurrences, 256 of whom died; 43 additional patients died during the study from other causes.

“There are more than one million colorectal cancer survivors in the United States,” says Van Blarigan, a member of the UCSF Helen Diller Family Comprehensive Cancer Center. “These individuals are living longer than ever before, but the disease remains the second leading cause of cancer death in the United States. There’s a pressing need for improved survivorship care and resources to help people adopt and maintain a healthful lifestyle after cancer diagnosis.

“Our research team is conducting clinical trials to evaluate the feasibility and acceptability of digital health lifestyle interventions for colorectal cancer patients,” Van Blarigan continues. “If our interventions are acceptable and useful to patients, we’ll test their impact on risk of cancer recurrence and mortality in future studies.”

UCSF oncologist Alan P. Venook, MD, is a coauthor and was involved in designing the original clinical trial. He’s the Madden Family Distinguished Professor of Medical Oncology and Translational Research, and the Shorenstein Associate Director for Program Development at the UCSF Helen Diller Family Comprehensive Cancer Center.

“This finding is a great example of lessons we can learn from studies even if the experimental treatment wasn’t an advance,” Venook says. “It also demonstrates the spirit of collaboration among cancer researchers who are determined to improve patient outcomes in any way possible.”

— Source: UCSF Helen Diller Family Comprehensive Cancer Center