Kids Gulp sept billion calories par an

C'est plus de 12,5 millions d'enfants. Et de nouvelles recherches dans le British Medical Journal suggère que les enfants obèses ont des facteurs de risque beaucoup plus élevés pour les maladies cardiovasculaires en tant qu'adultes.

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Gut microbes help the body extract more calories from food

ScienceDaily (Sep. 12, 2012) — You may think you have your food all to yourself, but you're actually sharing it with a vast community of microbes waiting within your digestive tract. A new study from the University of North Carolina School of Medicine reveals some gut microbes increase the absorption of dietary fats, allowing the host organism to extract more calories from the same amount of food.

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"This study is the first to demonstrate that microbes can promote the absorption of dietary fats in the intestine and their subsequent metabolism in the body," said senior study author John Rawls, PhD, associate professor in the Department of Cell and Molecular Physiology at UNC. "The results underscore the complex relationship between microbes, diet and host physiology."

Previous studies showed gut microbes aid in the breakdown of complex carbohydrates, but their role in dietary fat metabolism remained a mystery, until now. The research was published in the Sept 13, 2012 issue of the journal Cell Host & Microbe.

The study was carried out in zebrafish, which are optically transparent when young. By feeding the fish fatty acids tagged with fluorescent dye, the researchers were able to directly observe the absorption and transport of fats in the presence or absence of gut microbes.

The researchers pinpointed one group of bacteria -- Firmicutes -- as instrumental in increasing fat absorption. They also found the abundance of Firmicutes in the gut was influenced by diet: fish fed normally had more Firmicutes bacteria compared to fish that were denied food for several days. Other studies have linked a higher relative abundance of Firmicutes in the gut with obesity in humans.

"Our findings indicate that the gut microbiota can increase the host's ability to harvest calories from the diet by stimulating fat absorption," said the study's lead researcher, Ivana Semova, PhD, who was a graduate student at UNC at the time the study was conducted. "Another implication is that diet history could impact fat absorption by changing the abundance of certain microbes, such as Firmicutes, that promote fat absorption."

Although the study involved only fish, not humans, the researchers say it offers insights that could help inform new approaches to treating obesity and other disorders. For example, said Rawls, "If we can understand how specific gut bacteria are able to stimulate absorption of dietary fat, we may be able to use that information to develop new ways to reduce fat absorption in the context of obesity and associated metabolic diseases, and to enhance fat absorption in the context of malnutrition."

Study co-authors include Lantz Mackey of UNC, Juliana Carten and Steven Farber of the Carnegie Institution for Science, and Jesse Stombaugh and Rob Knight of the University of Colorado at Boulder.

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Scientists identify protein that stimulates brown fat to burn calories

ScienceDaily (May 10, 2012) — Scientists have identified a protein which regulates the activation of brown fat in both the brain and the body's tissues. Their research, which was conducted in mice, was published May 11, in the journal Cell.

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Unlike white fat, which functions primarily to store up fat, brown fat (also known as brown adipose tissue) burns fats to generate heat in a process known as thermogenesis. The research, led by scientists at the University of Cambridge Metabolic Research Laboratories at the Institute of Metabolic Science, discovered that the protein BMP8B acts on a specific metabolic system (which operates in the brain and the tissues) to regulate brown fat, making it a potential therapeutic target.

The scientists believe that activating brown fat could help to support current weight loss programmes, which individuals often struggle to maintain.

Dr Andrew Whittle, one of the authors of the paper from the Institute of Metabolic Science, said: "Other proteins made by the body can enhance heat production in brown fat, such as thyroid hormone but often these proteins have important effects in other organs too. Therefore they are not good targets for developing new weight loss treatments. However, BMP8B seems to be very specific for regulating the heat producing activity of brown fat, making it a more ideal mechanism for new therapies."

The experiments showed that when mice lacked the protein BMP8B they found it more difficult to maintain their normal body temperature. They also became much more obese than normal mice, particularly when fed a high-fat diet. Additionally, when the researchers treated brown fat cells with BMP8B they responded more strongly to activation by the nervous system. Furthermore, when BMP8B was administered to specific parts of the brain it increased the amount of nervous activation of brown adipose tissue. The result was that these BMP8B-treated brown fat cells burned more fat and mice given BMP8B in the brain lost weight.

Professor Toni Vidal-Puig, lead author of the study from the Institute of Metabolic Science and a member of the MRC Centre for Obesity and Related Metabolic Diseases, said: "A major feature of current weight-loss strategies is that people lose a lot of weight early on, but then reach a plateau despite continuing to follow the same diet regime. This is because the human body is incredibly good at sensing a reduction in food consumption and slows the metabolic rate to compensate. A strategy to increase brown fat activity could potentially be used in conjunction with current weight loss strategies to help prevent the typical decrease in a person's metabolic rate.

"One could be sceptical that techniques to increase metabolic rate might just be compensated by the body trying to make you want to eat more, to fuel this increased metabolism. But our findings showed that treating mice with Bmp8b did not have this effect, it simply made them lose weight by burning more fat in their brown adipose tissue.

"There are obvious differences between mice and humans, and from a therapeutic perspective this work is preliminary. Validation will be necessary to see if manipulating BMP8B would be safe and effective in humans."

The research was funded by the Medical Research Council (MRC), the Wellcome Trust, and the Biotechnology and Biological Sciences Research Council (BBSRC).

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