Brains could shrink as waistlines expand, scientists have warned.
Parts of the brain key to planning and memory are smaller in obese people than in their lean friends and neighbours.
The difference is so great that their brains appear up to 16 years older than their true age, a study of American pensioners found.
With brain shrinkage linked to dementia, the finding adds weight to the suspicion that piling on the pounds may raise a person's risk of Alzheimer's.
The University of California researchers created 3D maps from brain scans of almost 100 men and women in their 70s.
The heavier volunteers had smaller brains, with regions important for planning and memory particularly likely to be depleted, New Scientist reports.
The brains of the 51 overweight people were on average 6 per cent smaller than those of their normal weight counterparts, while those of the 14 obese volunteers were 8 per cent smaller.
Researcher Paul Thompson said: 'The brains of overweight people looked eight years older than the brains of those who were lean, and 16 years older in obese people.'
Type 2 diabetes, which is common in the overweight, is known to accelerate the ageing of the brain and the onset of dementia.
But the relationship between brain size and weight still stood when the researchers accounted for this, suggesting it is the fat itself that is causing the problem.
It is thought that high levels of fat raise the odds of the arteries clogging up, cutting the flow of blood and oxygen to the brain.
This could brain cells to die and the organ to shrink.
Further work by the same researchers shows exercise protects the brain levels at risk of shrinking, by upping blood flow.
Professor Thompson said: 'The most strenuous kind of exercise can save about the same amount of brain tissue as is lost in the obese.'
He believes that the high demands put on the brain areas used for memory and planning may make them more sensitive than others to changes in oxygen levels.
But others said the link was not clear cut.
Swedish researcher Deborah Gustafson said the brain areas studied are also involved in eating and metabolism.
This means that cell death there, for whatever reason, could lead to people eating more.
'There are not enough longitudinal data available for us to know which is the chicken and which is the egg,' she said.
OOH - DAILY MAIL, YO! SOURCE OF ALL HIGHLY RELIABLE NEWS! ;D
HAHA, YOU ARE A NAUGHTY STIRRER, YO! MOST ALZHEIMERS PATIENTS I'VE WORKED WITH ARE JOLLY SKINNY! AND ANOREXIA IS FAR MORE HARMFUL ON THE BRAIN THAN OBESITY.
BUT YES, LACK OF EXERCISE WILL HAVE A DETRIMENTAL EFFECT ON ALL ORGANS, AS THEY'LL RECEIVE LESS OXYGENATED BLOOD. AND BEING SIGNIFICANTLY OVERWEIGHT COULD IN QUITE A FEW CASES BE DUE TO SELF NEGLECT, WHICH COULD ALSO INCLUDE NEGLECT OF BRAIN USAGE, AND OF COURSE THE BRAIN NEEDS TO BE USED TO MAINTAIN GOOD FUNCTION. AND I'M SURE A LOT OF PEOPLE ARE BAD AT CONTROLLING WEIGHT DUE TO BEING BAD AT PLANNING IN GENERAL - SO NO WONDER THE PLANNING PART OF THEIR BRAIN (FRONTAL LOBE, YO!) IS SMALLER. SO RATHER THAN ONE CAUSING THE OTHER (CHICKEN EGG THING) THEY ARE LIKELY BOTH CAUSED BY THE SAME THING.
I think what they are really trying to imply here, is the fact that people should try and stay in shape. I really don't think that they would actually ask people to become anorexic. Though people that are anorexic and people that are obese are weak minded.
HAHA - GOSH, YOU ARE ANOTHER NAUGHTY DRAMA MONGER! ACTUALLY, IN TERMS OF MIND, OBESITY DUE TO LACK OF SELF-DISCIPLINE (TO WHICH I ASSUME YOU ARE REFERRING) IS ON THE OPPOSITE END OF THE SPECTRUM FROM ANOREXIA. ANOREXIA IS DUE TO INSISTENCE ON RIGOROUS SELF-DISCIPLINE TO THE DETRIMENT OF ONE'S HEALTH, DUE TO A STRONG NEED TO MAINTAIN CONTROL. IT HAS NOW BEEN LINKED TO GENETICS, YO, ALTHOUGH OF COURSE HAS A COMPLEX MIX OF CAUSES. OBESITY DUE TO LACK OF SELF-DISCIPLINE IS CAUSED BY PUTTING IMMEDIATE GRATIFICATION BEFORE LONG TERM GOALS - WHICH CAN BE CAUSED BY A SMALLER FRONTAL LOBE, OR INDEED FRONTAL LOBE DAMAGE, OR HABIT (WHICH MAY INDEED SHRINK THE FRONTAL LOBE - WHO KNOWS).
OF COURSE, EVERYONE SHOULD TRY TO STAY IN SHAPE. THAT IS A BIT DIFFERENT FROM MAKING THE SWEEPING STATEMENT THAT FATTIES HAVE SMALLER BRAINS, YO! AND OF COURSE THEY ARE NOT ASKING PEOPLE TO BECOME ANOREXIC - HOWEVER, IN STATING THAT FATTIES HAVE SMALLER BRAINS, THEY ARE SUGGESTING IT IS A WEIGHT CAUSE SPECIFIC TO FATTIES, YO, AND NOT THE EXTREME THINNIES. A MORE ACCURATE (ALTHOUGH OF COURSE LESS PROVOCATIVE AND THUS LESS ATTENTION-STRIKING) TITLE WOULD BE 'LACK OF EXERCISE CAN LEAD TO BRAIN SHRINKAGE'. ALTHOUGH THEY HAVEN'T ACTUALLY PROVED THAT, AS THERE IS NO INFO ON THE LIFESTYLE OF THE 100 PEOPLE THEY TESTED. THEY CLEARLY NEED TO RESEARCH MORE THOROUGHLY!