Bacteria in the Body: Helping Us Use Energy

By: Reyna Reyburn
May 17, 2011
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Over the past several decades, there has been a steady increase in obesity cases and many people have different opinions on the reason why. The human body has various complex systems that maintain homeostasis, and the digestion system is one of them. This includes the mouth, esophagus, stomach, small intestine, large intestine and rectum, but it also includes thousands of microbes; all of which have a vital role to play. Antibiotics kill these ‘good’ bacteria as well as the pathogenic ones and research has shown that the amount of certain bacteria may have a significant impact on weight.

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Bacteria have a specific role wherever they are on earth, whether they’re living in soil or in our body. In our body, studies have shown that they may prevent excessive weight gain. One study used 3 test groups of mice to determine how different levels of digestive bacteria have different effects on the rate of weight gain (Pennisi, 1). Obesity can lead to various other health conditions, such as diabetes and heart disease, which is why new findings about reversible and preventative measures are always helpful. Many people in our American culture fear being overweight yet don’t understand how the body works enough to avoid it as carefully as they wish. Worse, many people don’t know the processes that a body undergoes to shed excess weight, and therefore people choose extremely unhealthy diets. In this past year, I have learned a lot about the human body and how it utilizes food for nutrients. This new research on how microbes affect weight gain appears to be a promising new factor in maintaining a healthy weight.


H. pylori bacterium
H. pylori bacterium

Bacteria in the body:
There are many different types of bacteria in this system and each one plays a large role in the efficiency of absorbing nutrients and fat storage. One of these microbes includes H. Pylori: a curved rod bacterium that is most famous for causing peptic ulcers and stomach cancer in humans (Tortora 718). It thrives in our stomachs, where
most microbes are killed by the acidity, and a combination of antibiotics can destroy them (Tortora, 719) Over the past several decades, the number of people with this bacteria has declined, which is good because of the decrease in cases of ulcers and cancer of the stomach. But some studies have shown that H. Pylori might be responsible for helping to regulate the ghrelin hormone (Pennisi, 1). Ghrelin is what stimulates the brain to tell us that we’re hungry and need food. With less regulation of the hormone, people might be stimulated to feel hungrier more often, which would lead to weight gain. Another bacteria that naturally lives in the body is E. coli, one that we have used frequently in lab. It usually isn’t pathogenic, but some strains can cause urinary tract infections and severe diarrhea (Tortora, 310). Desulfovibrio is also found in the intestines of humans and animals. It is important to the body because it reduces sulfur or sulfate to hyrdorgen sulfide (Tortora 312).

Effects of Antibiotics:
Antibiotics are prescribed for ulcers caused by this bacterium but they also kill other, natural microbes in the body. Humans host many different types of bacteria and we benefit from them because their presence prevents the presence of harmful bacteria. This is called microbial antagonism because our microbes compete for nutrients and living space with bacteria that is trying to invade (Tortora, 401). Symbiotic relationships require stable conditions to ensure survival and equilibrium. As the equilibrium is disrupted because of antibiotics, the trend of disappearing microbes in the gut continues. An example of this is how farmers who raise livestock feed their animals antibiotics in order to reduce the amount bacterial infections and to accelerate their growth. These animals then lose their natural protection (flora) and also cause more resistant microbes to emerge (Tortora, 577). But farmers do this to own bigger (more profitable) animals who are not sick.

There are many different types of antibiotics
There are many different types of antibiotics

Research Studies:
A microbiologist named Martin Blaser in New York designed an experiment using lab mice to test this theory on weight gain. He fed one group a low dose of antibiotics over a long period of time, a second group a high dose of antibiotics over a short period of time, and a third group was the control. The mice with the low dosage had 15% more body fat than the control group, and the mice with the high dosage had 25% more (Pennisi, 2).

A study led by J.I. Gordon (2009) showed that obese rodents who had a low percentage of a specific bacterium gained more of it while losing weight (Tschöp 344). This bacterium, Bacterioidetes, has been shown to be “more efficient at harvesting dietary energy” (Tschöp, 344). Most bacteria in our stomachs are either Firmicutes or Bacteroidetes. However, studies done on mice do not always apply to humans because their genetics aren’t extremely similar. In another study done by Jeffrey Gordon, on a small group of 12 volunteers, “the obese volunteers had 20% more Firmicutes and nearly 90% less Bacteroidets than the leans ones” (Pearson, 2). This suggests that their lack of bacteria that help us efficiently use energy has caused a misuse of energy that has led to obesity.

Andrew Gewirtz and his team of researchers have found a connection between a lack of protein toll-like receptor 5 and being overweight (Lindner, 1). He used groups of mice without the receptor because its job is to keep potentially harmful bacteria under control. Without it, microbes overpopulate and cause intestinal cells to become inflamed. While the cells are inflamed, they can’t effectively absorb and process glucose. This can cause weight gain, high cholesterol, and high blood pressure (Park). These mice also ate more than the mice with the TLR5 (Park).

Bacteria Population in Obese Stomach
Bacteria Population in Obese Stomach

Preventing Obesity:
There are many healthy choices regarding diet and exercise that can prevent weight gain/promote weight loss that have been effective for many years. The most common solution is to consume a lower calorie, more nutritional diet and commit to regular exercise. The Amish seem to be an interesting focus of study for researchers because they all have such similar habits and share a small environment. The Amish also do a great deal of daily physical work, which burns a lot of calories (Wanjek 2008). Despite enjoying a large amount of fattening foods, such as pork with fat and gravy, a study showed that they walk an average of 18,000 steps per day (Wanjek 2008). This is much more physical activity than many other Americans do. One possible factor of the increase in obesity cases is the exponential rise in technology. For example, while Amish children might spend childhood playing physical games or doing strenuous chores, other children might spend all day on weekends playing video games or watching TV and occasionally mow their front lawn. The latter group of children grow up in a much more sedentary lifestyle and become very accustomed to it, which constantly influences their activity choices.

How people choose to live and what they eat influences every aspect of their body. The body responds by adjusting the populations of bacteria within it. Preventing weight gain may be as simple as taking a pill to selectively control the microbial population in the future if this research proves correct. But for now, preventing it as early as possible is recommended. By forming active and healthy eating habits as a child, it is easier to maintain it throughout life.

Literature Cited:
1. Lindner, B. “Study: Intestinal Bacteria May be Causing Obesity.” Published online in Digital Journal 1-2 (2010).

2. Park, A. “A Hidden Trigger of Obesity: Intestinal Bugs.” Published online in Time 1-2 (March 5th 2010).

3. Pennisi, E. “Girth and the Gut (Bacteria).” Published online in Science Vol. 332 no. 6025 pp. 32-33 (2011).

4. Tortora, Funke, Case 2010. Microbiology: An Introduction. Pearson Education Inc, CA.

5. Tschop, M; Hugenholtz, P; Karp, C. “Getting to the core of the gut microbiome.” Published in Nature 344-346 (2009).

6. Wanjek, C. “How Amish Avoid Obesity.” Published online in Life Science, 1 (2008).