Researchers from the University of California, San Francisco and University of Washington Medical Center have shown that consumption of a fat-rich diet increases the number of brain immune cells called microglia which triggers a local inflammation within the mediobasal hypothalamus (MBH) and causes an individual to eat more food, burn fewer calories, and gain more weight.
A series of experiments were conducted on two groups of mice. One group was fed a fat-rich diet for four weeks and the other with a healthier low-fat diet. Comparing the results, the group that was fed with fat-rich diet consumed more food, burnt fewer calories and exhibited substantial weight gain.
The researchers further gave the mice on a fatty diet an experimental drug called PLX5622 which depleted the number of microglia in the mice. These mice ate 15 percent less appetite and gained 20 percent less weight than untreated mice on the same diet.
The results were confirmed by giving microglial inflammation activating drug to the mice fed with healthy, low-fat diet. This resulted in the mice eating 33 percent more food, burning 12 percent less energy and 400 percent increase in weight gain.
“It can be confidently concluded that the inflammatory activation of microglia is sufficient to alter the regulation of energy balance in the hypothalamus, leading to overeating and weight gain,” said Joshua Thaler, associate professor of medicine at the UW Medicine Diabetes Institute and senior co-author of the study.