You might have thought resisting that piece of chocolate cake or extra biscuit was simply a matter of exerting a little will power.
But for some of us it’s much more difficult than that - because of the way our brains are wired.
Scientists have found that a key part of the brain which stops the body from acting on impulse - and gorging - does not function as well in those who are overweight or obese.
This means that when they open a tub of ice cream or packet of sweets, they are inclined to eat the lot.
Researchers from Yale University in the US showed photographs of burgers, biscuits, ice cream and brownies to 21 people, half of whom were obese.
When the subjects saw the pictures when they were hungry and their blood sugar levels were falling, the area of the brain that stops us acting on impulse - the prefrontal cortex - did not work as well.
But it worked far less well in the obese.
Professor Rajita Sinha, from Yale, whose study is published in the Journal of Clinical Investigation, said: “Their brains are different. This could explain why they are more vulnerable to high calorie foods.”
Another researcher, Dr Kathleen Page, said: “Our results suggest obese individuals may have a limited ability to inhibit the impulsive drive to eat, especially when glucose levels drop below normal.”
Last year Australian researchers claimed obese people’s brains were not able to send signals to their bodies to tell them to stop eating.
Reuters reports that
the study is part of a push to understand the underlying biological processes that contribute to obesity, which affects more than one third of adults and nearly 17 percent of children in the United States.
Researchers used functional magnetic resonance imaging, or fMRI, to examine areas of the brain that become active when a person views images of high-calorie foods, healthy foods like fruits and vegetables and non-food items. - Daily Mail, Reuters