Anyone who has ever tried to lose 5 percent of his or her body weight and sustain it, will be interested in the work of neuroscientist and obesity researcher, Michael Morabito, PhD. A post-doctoral researcher in the laboratory of Berrie Center Co-Director Rudy Leibel, MD, Dr. Morabito is mapping the regions of the brain that either respond, or fail to respond, to weight loss. The eventual goal is to find new targets for new treatments “that address the maintenance of a reduced weight,” said Dr. Morabito, “which is even more difficult than achieving a reduced weight loss.”
Dr. Morabito studies mice of normal weight that are given a high fat diet to become obese, as well as mice that are no longer obese after losing weight—to see how signaling changes in different regions of the brain during the process of weight gain and weight loss. Specifically Dr. Morabito and his team are looking for signaling from leptin, a hormone released by fat tissue, that tells the brain when you are full.
Said Dr. Morabito: “We’re examining the entire brain. We’re looking at areas of the brain that have been traditionally known to control feeding behavior, like the hypothalamus. But we’re also mapping new regions of the brain that have never been looked at before.”
So far, Dr. Morabito is finding what he expected—that the more weight the mice gain, the more difficult it becomes for their brains to detect the leptin signal. But the study also shows that after weight loss, the mice’s sensitivity to leptin has been permanently altered, returning to initial levels in only 7 of the 15 regions of the brain. Altered leptin sensitivity is one possible explanation for why obese mice (and people) have such a difficult time sustaining weight loss, said Dr. Morabito who, commented that over the past few years, he too has put on a pesky 15 pounds that his body now utilizes to arrive at a higher body weight “set point”
“We’re trying to understand the brain mechanisms underlying the setpoint, how your body decides the weight it wants to be,” said Dr. Morabito. “We’re hoping to one day be able to find regions of the brain where this signaling has changed during weight gain and loss. Then we can try to design the appropriate therapies so that people can sustain their weight loss.”