Genes make the fat hungry
Mar 24, 2003
Fat people should not be held to blame for their big appetites, a leading U.S. expert said.
Fat people should not be held to blame for their big appetites, a leading U.S. expert said.
Dr Jeffrey Friedman said some individuals were genetically “hard-wired†to feel hungry.
A key culprit was the hormone leptin, which inhibits appetite as body fat increases. Loss of body fat caused less leptin to be produced, stimulating a desire to eat more. Research by Friedman and other scientists had shown that genetic mutations linked to leptin were associated with obesity in some people.
A number of other hormones and genes also played a role in appetite and weight, orchestrating the unconscious urge to eat. Friedman said the power of these basic drives should not be underestimated. Friedman is director of the Starr Centre for Human Genetics, Professor at the Rockefeller University, and an investigator at the Howard Hughes Medical Institute. Writing in the journal Science, he said: “The feeling of hunger is intense and, if not as potent as the drive to breathe, is probably no less powerful than the drive to drink when one is thirsty.
Who is it that can resist a drink of cold water when their lips are parched? This is the feeling the obese must resist after they have lost a significant amount of weight.
The power of this drive is illustrated by the fact that, whatever one’s motivation, dieting is generally ineffective in achieving significant weight loss over the long term.â€
A predisposition to being overweight was a legacy of our genetic past, said Dr Friedman. Hunter-gatherers living where food was sparse would have benefited from obesity genes that increased their body energy stores and helped them through times of famine.
But the same genes would be harmful to those living in societies—such as Western civilisations — where the risk of starvation was low because of farming, domestication and the ability to store food. People in such communities were better off with genes that kept them slim.
In modern times, obesity and leptin resistance appear to be the residue of genetic variants that were more adaptive in our previous environments, said Friedman.
“It may be that the obese carry the hunter-gather’ genes and the lean carry the Western’ genes.â€
Another research showed that some people may literally have burgers on the brain and be addicted to junk food. Research with rats suggests that sugar and fat can “hook†the body in the same way as heroin.
If the controversial theory is confirmed, it could help explain soaring obesity rates in the West - and the phenomenal success of fast food outlets. Scientists have learned over the past 10 years that appetite is governed by complex systems involving a host of hormones and signalling molecules.
One hormone called leptin, for instance, is secreted by fat cells and sends an “I’m full†signal to the brain when enough has been eaten. Recent studies have indicated that people who gain weight become leptin-resistant. The fatter they are, the less the leptin signal is read, so they stay hungry.
Another brain chemical, galanin, has been shown to stimulate the body to want more fat and is produced in larger amounts the more fat is eaten, creating a vicious circle.
But now scientists have taken a step further by claiming that the body may actually become addicted to fat and sugar.
dpa
Dr Jeffrey Friedman said some individuals were genetically “hard-wired†to feel hungry.
A key culprit was the hormone leptin, which inhibits appetite as body fat increases. Loss of body fat caused less leptin to be produced, stimulating a desire to eat more. Research by Friedman and other scientists had shown that genetic mutations linked to leptin were associated with obesity in some people.
A number of other hormones and genes also played a role in appetite and weight, orchestrating the unconscious urge to eat. Friedman said the power of these basic drives should not be underestimated. Friedman is director of the Starr Centre for Human Genetics, Professor at the Rockefeller University, and an investigator at the Howard Hughes Medical Institute. Writing in the journal Science, he said: “The feeling of hunger is intense and, if not as potent as the drive to breathe, is probably no less powerful than the drive to drink when one is thirsty.
Who is it that can resist a drink of cold water when their lips are parched? This is the feeling the obese must resist after they have lost a significant amount of weight.
The power of this drive is illustrated by the fact that, whatever one’s motivation, dieting is generally ineffective in achieving significant weight loss over the long term.â€
A predisposition to being overweight was a legacy of our genetic past, said Dr Friedman. Hunter-gatherers living where food was sparse would have benefited from obesity genes that increased their body energy stores and helped them through times of famine.
But the same genes would be harmful to those living in societies—such as Western civilisations — where the risk of starvation was low because of farming, domestication and the ability to store food. People in such communities were better off with genes that kept them slim.
In modern times, obesity and leptin resistance appear to be the residue of genetic variants that were more adaptive in our previous environments, said Friedman.
“It may be that the obese carry the hunter-gather’ genes and the lean carry the Western’ genes.â€
Another research showed that some people may literally have burgers on the brain and be addicted to junk food. Research with rats suggests that sugar and fat can “hook†the body in the same way as heroin.
If the controversial theory is confirmed, it could help explain soaring obesity rates in the West - and the phenomenal success of fast food outlets. Scientists have learned over the past 10 years that appetite is governed by complex systems involving a host of hormones and signalling molecules.
One hormone called leptin, for instance, is secreted by fat cells and sends an “I’m full†signal to the brain when enough has been eaten. Recent studies have indicated that people who gain weight become leptin-resistant. The fatter they are, the less the leptin signal is read, so they stay hungry.
Another brain chemical, galanin, has been shown to stimulate the body to want more fat and is produced in larger amounts the more fat is eaten, creating a vicious circle.
But now scientists have taken a step further by claiming that the body may actually become addicted to fat and sugar.
dpa