Rates of obesity, especially amongst children, are causing considerable concern around the globe due to the link with a number of life threatening illnesses, including heart disease, diabetes and some forms of cancer.
While dietary approaches to weight loss are crucial to stemming the trend, research has also indicated that there could be genetic factors at play. However some have reached the conclusion that diet and genetics are not the only explanations, and there could be some primary neurological explanation.
The researchers on the new study, published online ahead of print in the Proceedings of the National Academy of Sciences, worked with rats that had been bred to have a difference in the feeding centre of the brain, and observed the differences in brain activity when the rats were fed a high fat diet.
In some, the neurons that are supposed to signal when an individual has eaten enough to burn calories were inhibited by other cells. In others, the satiety signalling neurons were much more active.
Lead researcher Tamas Horvath, chair and professor of comparative medicine and professor of neurobiology and obstetrics & gynecology at Yale School of Medicine, said:
"It appears that this base wiring of the brain is a determinant of one's vulnerability to develop obesity. These observations add to the argument that it is less about personal will that makes a difference in becoming obese, and, it is more related to the connections that emerge in our brain during development."
What is more, Horvath and the team noticed that after eating the high fat diet, the rats that were vulnerable to obesity were seen to develop inflammation in the brain, which the others did not.
“These data suggest that consumption of an HFD has a major impact on the cytoarchitecture of the arcuate nucleus in vulnerable subjects, with changes that might be irreversible due to reactive gliosis,” they concluded.
"This emerging inflammatory response in the brain may also explain why those who once developed obesity have a harder time losing weight," Horvath said.
Proceedings of the National Academy of Science, online ahead of print 2 August 2010
“Synaptic input organization of the melanocortin system predicts diet-induced hypothalamic reactive gliosis and obesity”
Tamas L. Horvath, Beatrix Sarman, Cristina García-Cáceres, Pablo J. Enriori, Peter Sotonyi, Marya Shanabrough, Erzsebet Borok, Jesus Argente, Julie A. Chowen, Diego Perez-Tilve, Paul T. Pfluger, Hella S. Brönneke, Barry E. Levin, Sabrina Diano, Michael A. Cowley and Matthias H. Tschöp