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"What has been observed in humans with regard to obesity is that there seems to be a difference in the number of kinds of bacteria in the gut," said Rob Knight of the University of Colorado, Boulder. "That number is much lower in obese people than in healthy people."
Researchers have also seen differences in bacteria between mice bred to be obese versus those of normal weight. In one experiment, researchers found that an obese mouse's gut microbes extracted more of the calories from a given parcel of food than did those of non-obese mice.
This caused the obese mice to gain more body fat than the non-obese mice did.
But even stranger, in a type of mouse with a different mutation that leads to obesity, transferring gut microbes from the obese mice into other mice led the non-obese mice to eat more.
"They're not any better at extracting energy from the food. They're just hungrier apparently," Knight said. "There are more microbial cells in your body than there are brain cells. They may be outvoting you when it comes time to order (at the restaurant)."
If gut microbes can tell mouse brains to eat more, could they have other effects on the brain? Researchers are finding that the answer is yes.
"The exciting angle to this new study by Cosava et al has shown that it is not just the type of gut bacteria present that leads to increased fat storage but that the obese bacteria gut profile leads to changes in intestinal nutrient sensors and gut peptides, such as ghrelin, cholecystokinin, glucagon-like peptide 1 and peptide YY, that are involved in regulating appetite. In fact increases in ghrelin have been shown to increase the appeal of high calorie foods so this may explain why some people choose chocolate cake over salad – it’s not just all in the mind! Cosava’s study is yet to be formalised in humans but it shows that gut bacteria are likely to influence not just physiological reasons why some people gain weight but also what drives some people to overeat and have uncontrolled appetites, thus making weight loss so difficult."
"Gut bacteria could 'control' our urge to eat too much - and even make us anxious until we give in and have a snack, says a University of Colorado bacteria expert.
Obese people have different bacteria in their guts than others. Those they have consume more energy - and may prompt their 'hosts' to do the same.
'They're not any better at extracting energy from the food. They're just hungrier apparently,' said Rob Knight of the University of Colorado.
'There are more microbial cells in your body than there are brain cells. They may be outvoting you when it comes time to order at the restaurant.
'What has been observed in humans with regard to obesity is that there seems to be a difference in the number of kinds of bacteria in the gut. That number is much lower in obese people than in healthy people.''