Researchers can use functional MRI (fMRI) to examine how brain circuitry influences how much food a person eats, regardless of appetite, which may help identify new treatments for obesity, according to a study published in the October issue of the journal, Nature.
“The hypothalamus and brainstem are thought to be the principal homeostatic brain areas responsible for regulating body weight,” said Rachel Batterham, MD, one of the authors of the study conducted at the University College London, United Kingdom.
In prior research, Batterham and her colleagues showed that a hormone called peptide YY or PYY, released by the stomach in proportion to the number of calories eaten, is a powerful appetite suppressant. Previous experiments showed that treating normal and obese subjects with intravenous PYY decreased food intake by up to 30 percent.
Eight subjects, who had fasted for 14 hours prior, were scanned twice using fMRI; once while on an intravenous drip of PYY; and once while receiving a saline solution.
Approximately 30 minutes after being scanned, Batterham had her subjects eat a buffet of their favorite meals. Results showed that those who received PYY ate an average of 25 percent fewer calories than the control group.
The fMRI scans of those patients showed that PYY not only lit up the hypothalamus but it increased activity in the orbital frontal cortex (OFC), the area of the brain associated with reward and pleasure. For patients on the saline drip, hypothalamus activity predicted caloric intake. But for those subjects who received PYY, it was the OFC.
According to the study, “the presence of a postprandial satiety factor switches food intake regulation from a homeostatic to a hedonic, corticolimbic area. An increased understanding of how such homeostatic and higher brain functions are integrated may pave the way for the development of new treatment strategies for obesity.”