bacterial ecology

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my comment : this explains why some people lose weight when they start drinking REAL MILK

Digestive germs more efficient in fat people than in thin, new papers suggest

Obese people have higher levels of an unusually efficient bacteria that thin people, offering a possible explanation for why they get fat, researchers reported Thursday.

Bacteria are needed in the stomach to help convert otherwise indigestible foods into a usable form, and the bacteria in obese people are better at the process, a team from Washington University in St. Louis reported in two papers published in the journal Nature.

In effect, obese people obtain more energy than lean people from the same amount of food, and those extra calories are being deposited on their waists.

The same disparity is found in mice, and giving lean mice the bacteria from fat animals caused them to gain weight, the researchers said.

If the findings hold up, it could lead to new ways to induce weight loss, or even to prevent weight gain in the first place.

"This is a potentially revolutionary idea that could change our view of what causes obesity and how we depend on the bacteria that inhabit our gut." wrote Matej Bajzer and Dr Randy J. Seely of the University of Cincinnati in an editorial accompanying the paper. "But a great deal remains poorly understood."

The proliferation of the efficient bacteria might be the result of obesity and not its cause, said Atkinson of the Obetech Obesity Research Center in Richmond Va., who was not involved in the research.

"If they are right, this could really be a significant advance", he said. "But I am not sure they are interpreting their data right. Correlation is not causation."

Neurobiologist Hans-Rudolf Berthoud of Louisiana State University's Pennington Biomedical Research Center in Baton Rouge, who also was not involved in the research, agreed. "This doesn't show that the bacteria cause obesity, absolutely not," he said.

More likely, he said, is that hormonal changes caused y losing weigh alter the distribution of bacteria. "I am a strong believer that the obesity crisis is caused by the rapid change in environment and lifestyle," Berthoud said.

An estimated 65 per cent of American adults are overweight and half of those are considered obese. The proportion of children who are overweight has gone from seven per cent to 15 per cent over the past 20 years, while the proportion of overweight adolescents has risen from fiver per cent to almost 16 per cent.

Intestines contain trillions of bacteria, perhaps 10 for every cell in the body. Almost 90 per cent of the bacteria fall into two major divisions, or phyla ; the Firmicutes and the Bacterioidetes.

Dr Gordon and his colleagues at Washington University had shown previously that obese mice have a higher proportion of Firmicutes and correspondingly small proportion of Bacteriodetes than their lean littermates.

In one of the two Nature papers, Gordon and graduate student Turnbaugh analyzed the genes in the different phyla of bacteria. The concluded that the Firmicutes are more efficient at digesting food that that body can't, such as the complex sugars in grains, fruits and vegetables, breaking them down into simple sugars used byn the body.

In the second study, Gordon and microbial ecologist Ruth Ley studied 12 obese people who lost weigh over the course of a year. They reported that the proportions of bacteria in their digestive system, initially similar to that of the obese mice, changed as the subjects lost weight, with the number of Firmicutes decreasing and Bacteriodetes increasing.

By H. Maugh II

Los Angeles Times