UCLA study reveals biological sex affects motivations for overeating
By Xinchen Li
June 8, 2017 1:47 a.m.
New research suggests that people with obesity have different eating habits due to their sex.
This new finding indicates medical professionals should take sex differences into account when designing future obesity treatments, said Arpana Gupta, principal investigator of the study and assistant professor at the David Geffen School of Medicine at UCLA.
Gupta said the researchers in the study now aim to test if current nutrition therapies have different effects on obese men and women.
Adult females in the United States have higher rates of morbid obesity, Gupta said. But the obesity rates in males have increased rapidly in the past 10 years and are now almost at the same rates as those in females.
“It’s not (that) men are not obese,” Gupta said. “They are obese, but in a different way due to their different eating habits.”
Doctors currently treat obesity by individualizing healthy diets for patients based on their body fat distribution and eating habits, said Zhaoping Li, chief of the Division of Clinical Nutrition at the Ronald Reagan UCLA Medical Center.
“We have known men and women have physiological differences, but (Gupta’s) research indicates sex differences also take place in the brain,” Li said.
Gupta’s study investigates brain activities of people with and without obesity in the reward, salience and sensorimotor networks, Gupta said.
The reward network controls dopamine release, which influences the appetite, Gupta said. The salient network integrates external and internal information of human body and the sensorimotor network processes sensation awareness and generates motor responses.
The study shows people with obesity in general tend to have intense activities in the reward and salience networks, Gupta said. In particular, obese females experience more changes in the reward and salience networks while obese males experience more changes in the sensorimotor network.
Li said her previous study shows patients will become healthier if they replace the regular fat in their meals with some amount of avocado fat, a unique kind of fat. She plans to collaborate with Gupta to study if male and female patients who participate in the avocado therapy will experience different brain activities.
Gupta said by studying people’s brain activities that are related to excessive eating, researchers can now explain men’s and women’s different eating habits.
“For instance, women tend to eat more meals throughout a day (when they feel emotional) whereas men will eat a big meal in one sitting (when they feel hungry),” Gupta said.
The abnormal brain activities related to overeating are part of a dynamic brain-gut interaction, said Emeran Mayer, one of the researchers and a professor at the David Geffen School of Medicine. People first feed the gut with high-calorie food, and the gut then send signals back to the brain that reinforce overeating.
One potential reason that many common treatments of obesity are not effective is they do not interrupt the brain-gut communication loop, Mayer said.
Gupta’s finding proves men’s and women’s brains are structured and function in different ways, which leads to differences in brain-gut interaction between males and females, Mayer said.
“I guess sometimes we have to admit men and women are physically different,” Mayer said.