You’re on your diet. As we have shown previous blog posts, not only are you super hungry (see post) but dopamine is firing too (see post). But added to the mix, scientists have found that another hormone may be responsible for our desire for eating high calorie foods. How does the hunger affect the way we eat?
Ghrelin the Hunger Hormone
Ghrelin the hunger hormone gets produced in the hypothalamus and triggers when other hormones such as leptin and insulin are reduced in the body. Leptin (produced in fat cells) and Insulin (produced in the pancreas) tell the brain that there’s not enough energy in the body and that it needs to do something quick smart about. Enter Ghrelin. It increases the need to eat by increasing our hunger.
How Do Calorie Restricted Mice Respond to Ghrelin?
Recent research has shed some light into why we might like to eat a bucket of hot chips for dinner while we’re on our diet. Researchers at the University of Texas studied mice to see if Ghrelin had any influence on the type of food they selected. They put the mice onto a calorie reduced diet and conditioned them for 12 days to go into two chambers, one with a high calorie food and the other with just ‘Regular Chow’. After the conditioning period they let them have free reign to see what chamber they went into and the majority chose the high calorie food chamber.
To see if it was Ghrelin that was responsible they did two tests. The first was to inject the mice with a compound that blocked the Ghrelin receptor. This means that the mice were no longer responsive to Ghrelin. What they found that the mice equally ate regular chow and the high calorie food.
The second experiment they took mice that had no Ghrelin receptor to see what these mice did. They found that they also equally chose the regular chow and the high calorie food.
The study shows the influence of Ghrelin on food reward in mice.
Can we extrapolate this to humans?
Many studies use mice before human studies and these are very good at understanding what might happen in humans. One thing that mice studies do is that they can inspect the brain something that you couldn’t do in humans. This would mean that a person who is on a restricted diet may desire to have a high calorie food in order to return to homeostasis, something that the body loves to do when your’re on a diet. It will be interesting to see how this plays out and if they can do a similar study in humans.
Mario Perello, Ichiro Sakata, Shari Birnbaum, Jen-Chieh Chuang, Sherri Osborne-Lawrence, Sherry A. Rovinsky, Jakub Woloszyn, Masashi Yanagisawa, Michael Lutter,and Jeffrey M. Zigma, ‘Ghrelin increases the rewarding value of high fat diet in an orexin-dependent manner’, Biol Psychiatry. 2010 May 1; 67(9): 880–886