BOSTON – Evidence from a twin study points to genes, rather than just adiposity, as the underlying factor in differences in appetite and satiety that have been observed in obesity.
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The work adds a new dimension – and some questions – to previous research, which suggested individuals with obesity show heightened brain activation to food cues, especially calorically dense food.
“We thought it was fat mass…but when we controlled for everything that monozygotic pairs have in common, that relationship went away, implicating something that the monozygotic twins have in common, i.e., genetics,” said first author Jennifer Rosenbaum, MD, in a video interview at the annual meeting of the American Academy of Clinical Endocrinologists.
Dr. Rosenbaum, a fellow in the department of metabolism, endocrinology, and nutrition at the University of Washington, Seattle, and her collaborators made use of a statewide twin registry to conduct an extensive investigation of subjective and objective measures of appetite and satiety in the 42 twin pairs.
Twins had a mean age of 31 years; 27 of the twin pairs were monozygotic, Dr. Rosenbaum said. At least one member of each twin pair met criteria for obesity, and participants had a mean body mass index of 32.8 kg/m2.
On the study day, participants arrived in fasting state, and had a fixed-calorie breakfast equivalent to 10% of their daily caloric needs. They then underwent dual-energy x-ray absorptiometry scanning to determine adiposity, and also filled out a behavioral questionnaire.
Then, participants received the first of two functional MRI scans; during the scan, they were shown images of high calorie foods, low calorie foods, and nonfood objects, completing ratings of how appealing they found each image. After consuming another standardized meal equivalent to 20% of daily caloric needs, the fMRI scan was repeated.