‘Hunger hormone’ turns eating less into eating more

University of Southern California Health News, 12/17/2015

If scientists can suppress ghrelin’s activity in the brain, they may be able to cut down on the desire to overeat. Looking to avoid overeating during those big holiday meals? You might want to avoid fasting in the days beforehand. Cycles of food restriction unleash a “hunger hormone” that increases the capacity to eat more before getting full, according to laboratory research by USC researchers. The insights published in the journal eLife could be valuable for helping the researchers develop new weight–loss therapies. Kanoski, doctoral student Ted Hsu and their colleagues conducted their studies in rats, but the work could have implications for humans. The researchers found that when they limited the time rats had access to food every day, the rats gradually were able to double their food intake to compensate. Over several days, the scientists allowed rats to eat only during a four–hour window, followed by 20 hours without food. The repeated short fasts sparked the hormone ghrelin to go into action before the anticipated feeding time. That hormone reduced rats’ feeling of fullness when they were eating, so they could eat more. The hormone’s action makes sense as an adaptive response: To get through times of scarcity, the brain enables the body to take in more calories during times of plenty. But that response isn’t so relevant in the well–fed Western world anymore, Kanoski said. “Instead, we need to find new ways to help us fight some of the feeding responses we have to external cues and circadian patterns.” The USC team’s study provides a rare look at the way ghrelin communicates with the central nervous system to control how much food is consumed.