THE LINK BETWEEN GUT BACTERIA AND OBESITY By
MILES KAUFMAN JEAN KIM
In the United States, where calories are readily available, the evolutionary mechanisms intended to avoid starvation have somewhat backfired. With the expansion of fast food options and sedentary lifestyles, there have been a higher instances of obesity-related health problems like heart attacks and diabetes across the country1. Interestingly, obesity is one of the only diseases in which the microbiome of the gut is directly associated with the pathology3. Inside our large intestines sit trillions of bacteria including E. coli and E. faecium that serve important symbiotic roles in our biological systems. Our gut bacteria don’t just sit in our intestines and break down molecules like fiber. They also cause cravings and influence how fat is stored and broken down. Over the past decade, many scientists have been working hard to discover how exactly our microbiomes influence our diets and susceptibility to weight gain. One key role our gut microbiome plays in our digestive system is processing dietary polysaccharides, commonly known as starch. In one study conducted by Dr.
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Fredrik Bäckhed, Swedish expert in microbiology and mouse physiology, investigated gut microbiota influence on fat deposition and storage4. The experiment consisted of two distinct mice colonies, the first of which was kept in a sterile, bacteria-free environment for eight weeks, while the second colony was fed the same diet in a non-sterile environment. After eight weeks, the mice belonging to the non-sterile environment with normal microbiome growth experienced a 42% increase in body fat, and their fat pads were 47% larger than the sterile mice. When the sterile mice were given microbes from the other group of mice, they had a 57% increase in body fat. This increase was seen even when the mice were given less food. Therefore, the study concluded that the presence of a gut microbiome was directly related to fat storage in mice, leading scientists to believe that bacteria are needed for proper fat storage even in humans4. Although the microbiome plays a major role in weight gain and weight loss, there are also genetic markers attributed to obesity. In
an experiment by Ussar et al., mice that were either obesity prone or obesity-resistant were studied for possible connections between microbiome and metabolism. When the researchers fed their mice with high-fiber diet, they showed weight gain, insulin resistance, and hyperglycemia. Even mice that were genetically resistant to obesity developed some of these symptoms5. When looking at the gut microbiota of the experimental mice, Ussar et al. found correlations between prevalence of certain bacteria species and weight gain. For example, mice with more M. schaedleri were on average leaner, and mice with more A. muciniphila experienced metabolic benefits including weight loss, reduced inflammation, and higher glucose tolerance. While obesity-resistant mice were healthier even with obesity-prone microbiomes, their genetics didn’t protect them from the medical and microbial side effects of an unhealthy diet. Dr. Ussar’s study concluded that while genetic factors can counteract an obesity-prone microbiome to an extent, having the wrong type of
