Twins with higher BMI show decreased brain activity while viewing high-calorie food

Identical twins with different body weights experienced different brain responses when viewing high- and low-calorie foods, with the heavier siblings experiencing decreased brain activation while viewing high-calorie food pictures vs. their lower-weight twins, according to study findings presented at the 51st European Association for the Study of Diabetes Annual Meeting.

In a cross-sectional study of monozygotic twins discordant for BMI, researchers also found no brain activity differences between twins while viewing food and nonfood pictures combined.

“There is a lot of evidence that the brain is important in the regulation of food intake and appetite, and is also [important] in the etiology of obesity,” Stieneke Doornweerd, MD, of the Diabetes Center at VU University Medical Center in Amsterdam, said during a presentation. “And it has been suggested that the excessive eating in obesity is a result of altered brain response in response to food cues in brain areas that are involved in reward ... but also in areas that are involved in impulse control, such as the lateral orbitofrontal cortex.”

Doornweerd and colleagues analyzed data from 16 monozygotic twin pairs from the Netherlands Twin Register, with a mean age of 49 years and a mean BMI difference of 3 kg/m². After an overnight fast, participants underwent functional MRI to measure brain activity in response to visual stimuli. Researchers presented participants with pictures of high-calorie food, low-calorie food and nonfood items shown in a block design.

Researchers measured activation in the limbic brain areas when viewing the images, including the amygdala, insula and orbitofrontal cortex, measured by changes in blood oxygen level dependent (BOLD) signal.

When comparing leaner and heavier twins, researchers found no differences in brain activation when viewing food vs. nonfood pictures. However, when viewing high-calorie food vs. nonfood pictures, the heavier twins showed decreased brain activation compared with their leaner sibling in the right orbitofrontal cortex — which is the center involved in inhibitory control — left insula and left caudate nucleus, according to Doornweerd.

“The fact that these findings were done in monozygotic twins ... implies that these findings are independent of genetic effects, and this must be a result of the exposure of unique environmental factors,” Doornweerd said. “These results suggest that the previous responses [in past studies] are probably influenced by genetic factors, and the higher control must have been a result of the influence of unique environmental factors.” – by Regina Schaffer

Reference:

Doornweerd, S, et al. Abstract #141. Presented at: 51st EASD Annual Meeting; Sept. 14-18, 2015; Stockholm.

Disclosure: Doornweerd reports no relevant financial disclosures.