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Is Eating Behavior Manipulated by the Gastrointestinal Microbiota? Evolutionary Pressures and Potential Mechanisms

It would appear that the bacteria that lives within us may contribute to (control) our daily food intake and moods, that is, according to a new study published this week in the journal BioEssays

Microbes in the gastrointestinal tract are under selective pressure to manipulate host eating behavior to increase their fitness, sometimes at the expense of host fitness. Microbes may do this through two potential strategies: (i) generating cravings for foods that they specialize on or foods that suppress their competitors, or (ii) inducing dysphoria until we eat foods that enhance their fitness. We review several potential mechanisms for microbial control over eating behavior including microbial influence on reward and satiety pathways, production of toxins that alter mood, changes to receptors including taste receptors, and hijacking of the vagus nerve, the neural axis between the gut and the brain. We also review the evidence for alternative explanations for cravings and unhealthy eating behavior. Because microbiota are easily manipulatable by prebiotics, probiotics, antibiotics, fecal transplants, and dietary changes, altering our microbiota offers a tractable approach to otherwise intractable problems of obesity and unhealthy eating.

What I particularly find interesting is how the microbes influence the vagus nerve. They mention in the article that severing (or blocking) the vagus nerve in mice induced a considerable amount of weight lost, indicating that the microbes influence our predisposition to obesity to gain their desired nutrients.

In combination of that, the microbes also seem to possess the ability to create neurochemicals that are analogous with mammalian hormones that are involved with mood and behavior.

More than 50% of the dopamine and the vast majority of the body’s serotonin have an intestinal source. Many transient and persistent inhabitants of the gut, including Escherichia coli, Bacilluscereus, B. mycoides, B. subtilis, Proteus vulgaris, Serratia marcescens, and Staphylococcus aureus have been shown to manufacture dopamine. Concentrations of dopamine in culture of these bacteria were reported to be 10–100 times higher than the typical concentration in human blood

The loss (or lack) of microbiota reduces the predisposition to obesity, hinting that a non diverse ecosystem of gut bacteria may be a factor in obesity.

For example, mice that lacked the toll-like receptor TLR5 became obese and developed altered gut microbiota, hyperphagia, insulin resistance, and pro-inflammatory gene expression.

Certain strains of probiotics on the other hand have been reported to reduce fat mass and improve insulin sensitivity and glucose tolerance, resulting in higher gut diversity. The reason a higher gut diversity is thought to lead to weight lost or the elimination of “food cravings” is due in large part to the increase competition and cooperation between the various species of bacteria, resulting in expenditure of their resources to manipulate their host.

Obviously there is more to all of this than what i have chosen to write here and so I highly recommend giving this research a read and I’d love to hear varying opinions!

Let me know what you think!




Science Daily

RESEARCH ARTICLE (without the annoying paywall)

Source: anthrojoyce

Reblogged from betterknowamicrobe | Originally from anthrojoyce

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    Hahahaha I like the way you think, but no, not necessarily. First, theoretically, it would have to be a probiotic...
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August 20, 2014   |   152 notes