Scientists have found a “switch” in the brain that helps to control appetite, which could explain why some people find it hard to know when to stop eating, a study has suggested.
The researchers believe that sugar levels in the bloodstream are involved in triggering when the switch is turned on during a meal so that people begin to feel full. But when the switch fails, it leads to overeating and obesity, they suggested.
The findings, which could provide further scientific evidence to support George Osborne’s new sugar tax, are part of a wider body research into the nature of appetite control and how hormones and brain activity are both involved in determining hunger, craving and over-eating.
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Scientists discovered the appetite switch while studying the strength of the connections between nerve cells in the brains of laboratory mice, a phenomenon known to be important for learning and memory.
In particular they wanted to see what would happen when the gene for an enzyme called OGT was deliberately knocked out in certain regions of the mouse brain.
OGT is known to be involved in many aspects of body metabolism, including the use of the hormone insulin and glucose in the bloodstream – which can rise during a meal or after drinking sugary drinks.
One of the jobs of the enzyme is to add a chemical derivative of glucose to proteins and this appears to be important certain nerve cells of the appetite control centres of the brain. When the gene for this enzyme is deleted or knocked out, the mice doubled in weight in just two weeks as a result of a build-up of fat.
“These mice don’t understand that they’ve had enough food, so they keep eating,” said Olof Lagerlof, a Johns Hopkins researcher and first author of the research published in the journal Science.