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How Gut Bacteria Help Make Us Fat and Thin

About 35% of American adults are struggling with obesity. We all know that the main reasons for their obesity come from a sedentary lifestyle, an unhealthy diet, and maybe some unlucky genes. Nevertheless, it the past couple of years, researchers have become more and more convinced that there’s another reason for obesity which hides in our bowels- gut microbes in abundance (billions on billions).

The microscopic residents in our intestines have been always helping us to decompose tough plant fibers, while living in such a nutritious place. However, their roles now seem to be more than this. The gut bacteria change the way we balance the glucose levels in blood, how we store fat, and how we react to hormones which make us feel full or hungry, according to latest evidences.

Luckily, researchers are now starting to understand the differences between the healthy mix and the wrong one, and the certain factors which make those differences. What researchers hope is that they will get to know how to cultivate our inner ecosystem so that it could ward off and even treat obesity. According to doctors, obesity is having a mass index, the height and weight ratio, higher than 30.

So for example, imagine baby formulas, foods, or supplements made to suppress the harmful microbes and promote the virtuous ones. Jeffrey Gordon of Washington University in St. Louis thinks researchers should consider creating foods from the inside out. So the intangible secret to control our weight might be keeping the microbes in our gut satisfied.

An Inner Rain Forest

Although researchers have already known that there are different types of microorganisms in our body, in the past decade they have discovered that the number of these microbes is so big that they actually outnumber human cells ten to one. It was discovered that the biggest and most various types of microbes live in the large intestine and mouth, but other huge microbes communities reside on our skin and in the genital tract.

The human being gathers the first unique group of microbes when it passes through the mother’s birth canal, and then it continues assembling new members from the surrounding throughout life. The various microbes are collectively regarded as the microbiome, and researchers have analyzed their genes and identified a lot of the most common inhabitants, despite the fact that they can vary individually and among human populations.

Studies which focused on comparison between intestinal bacteria in lean and obese individuals, have discovered that gut microbes can have a role in obesity. Studies which involved twins who were both obese or both lean, showed that the intestinal bacteria in lean people resembled a rain forest with different species, as oppose to that of the obese people, whose gut community was less diverse, resembling pond overloaded with nutrients with few dominating species.

For example, it was discovered that lean people usually have a greater variety of Bacteroidetes, which is a wide microbe tribe responsible for decomposing bulky plant fibers and starches into smaller molecules that can be used as an energy source by the body.

However, it doesn’t mean that these differences cause obesity. Gordon and his team wanted to show the cause and effect, so they conducted a series of experiments made on “humanized” mice, which were published in Science the last September They used a germ-free environment to raise genetically identical baby rodents, so their bodies were completely free of any bacteria. After that, the rodents’ guts were populated with intestinal microbes gathered from lean women and their obese twin sisters (1 set of identical female twins and 3 pairs of fraternal twins were used in these studies).

Although the researchers gave the same diet to the mice, those with the gut bacteria from obese twin had more body fat and grew heavier than those who got intestinal microbes from the lean twin. Not surprisingly, the obese mice had a less diverse gut microbe community

Gordon and his colleagues repeated this experiment with a little change. After dividing the baby rodents in 2 groups and giving them the gut microbes from their respective twins, they put all mice in a shared cage. In this experiment all mice stayed lean. The study demonstrated that the mice with gut microbes from obese people had received some of the gut bacteria of their roommates, especially Bacteroidetes varieties. This happened probably because they ate the feces of their roommates, a disgusting mouse habit.

Researchers wanted to further prove this fact, so they transferred 54 types of bacteria from thin mice to the mice with germs community from obese people, and discovered that the mice which were supposed to be obese got a healthy weight. As Gordon explains, these experiments prove the cause and effect relationship, and that preventing the obesity was possible.

He further states that the intestinal microbes in obese mice has specific “job vacancies” for those microbes which do key roles in preserving a normal metabolism and a healthy body weight. Gordon’s studies and other similar to his, give alluring clues about these specific roles. The fat mice in Gordon’s experiment had higher levels of substances called acylcarnitines and branched-chain amino acids, as oppose to the thin mice. Both these substances are usually increased in obese people and those with Diabetes Type 2.

Other job vacancy related to obesity could be that typically filled by Helicobacter pylori, stomach bacterium. Martin Blaser’s research from the New York University explains that it aids in the regulation of appetite by regulating the levels of the hunger-stimulating hormone called ghrelin.

Diet has a significant role in the formation of the gut ecosystem. For instance, a diet consisted of highly processed foods has been related to a less diverse intestinal bacteria in people. The complex interaction between microbes, food, and body weight was demonstrated by Gordon and his colleagues, by giving their “humanized” mice unhealthy diet which was low in fiber, vegetable and fruit and high in fat. The mice who had obese-type of gut microbes continued to grow fat even after housed together with the lean mice. The virtuous bacteria was somehow prevented to move in and flourish by the unhealthy diet.

The gut bacteria and diet interaction can predispose people to obesity from the moment they are born, as well as the methods of childbirth. According to studies, babies delivered by cesarean section and those which are fed with formulas, have higher risk for diabetes and obesity than babies delivered vaginally and those who are breast-fed. Maria Gloria Dominguez-Bello of N.Y.U and Rob Knight of the University of Colorado Boulder discovered that as newborns pass through the birth canal, they swallow some bacteria which is beneficial for digesting milk.

As oppose to them, babies delivered by cesarean section don’t go through this bacterial baptism. Moreover, formula-fed babies don’t receive the substances found in breast milk which nurture good bacteria and prevent colonization by bad bacteria. A recent Canadian study showed that formula-fed babies have gut bacteria unusual for breast-fed babies until they start consuming solid food. Dominguez-Bello explains that the presence of that bacteria prior to maturing of the gut and immune system can be a reason why these babies are more prone to asthma, allergies, celiac disease, eczema, and obesity.

A late recognition of the influence of gut microbes on body weight has increased the concern about the wasteful use of antibiotics in kids. Blaser demonstrated that low doses of antibiotics given to young rodents, similar to what livestock is given by farmers, make them develop about 15% more fat than those which haven’t received such drugs. Some of the bacteria which help people preserve their healthy body weight can be obliterated by antibiotics.

Beyond Probiotics

A lot of scientists dealing with microbiome believe their research will motivate a new generation of tools to prevent and treat obesity. However, researchers say that this is a young field and that there are many more questions than answers. Claire Fraser of the University of Maryland says that the collected information from human studies are much messier than that of mouse studies. She is studying the gut microbes and obesity in the Old Order Amish people. Although Amish are homogeneous population there’s still a large individual variation which hampers the isolation of the microbiota role in disease such as obesity.

Nevertheless, many scientists are constantly creating potential treatments. For instance, Dominguez-Bello’s clinical trial in Puerto Rico involves babies delivered with C- section who are straightaway swabbed with gauze cloth contaminated with small amounts of the vaginal fluids of their mother, and resident microbes. The overall health and weight of the babies will be tracked by Bello, and will be compared with the babies delivered with cesarean section but without the gauze treatment.

An Amsterdam researchers are investigating whether weight loss can be obtained when feces form thin people is transferred to overweight people. But these “fecal transplants” are regarded and risky and imprecise by the researchers in U.S. Robert Karp from the National Institutes of Health says that more promising and safe approach would be to determine the exact bacteria strains related to leanness, identify their roles thus creating appropriate treatments.

Gordon has suggested adding beneficial bacteria and nutrients required to establish them in our gut in foods. This is somewhat a scientific version of the modern probiotic yogurt. Although researchers in this field don’t believe that the war on obesity can be conquered by probiotics alone, it turns out that along with eating right and exercising we should engage our inner army of microbes.

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