This paper examines the relationship between commensal gut bacteria and the growing obesity epidemic in developed nations. Drawing on research into the human microbiome, the paper explains how bacteria such as Bacteroides thetaiotaomicron and Helicobacter pylori contribute to digestion, appetite regulation, and metabolic control. It argues that Western medical practices — particularly the widespread use of antibiotics and C-section deliveries — have significantly depleted these beneficial bacterial populations, especially in children. The paper connects this microbial disruption to rising obesity rates over the past three decades, and briefly notes emerging research suggesting the microbiome may also influence stem cell differentiation into fat versus muscle or bone tissue.
A global obesity epidemic is having a major impact on the healthcare costs of developed nations (Brody, 2011). For example, the annual healthcare cost of obesity in the U.S. is estimated to be $150 billion (Hurt, Kulisek, Buchanan, and McClave, 2010). This epidemic has been blamed on a powerful fast food and beverage industry, the comparatively low cost and convenience of these foods, and the increased prevalence of sedentary lifestyles. Another less obvious cause may be Western medicine. This essay describes the role Western medicine may be playing in promoting an obesity epidemic.
An adult human body contains approximately 60 to 90 trillion cells (Iyer, n.d.), but the bacterial contribution is ten times that number (Ackerman, 2012). While most of the bacteria reside in the colon, scientists are discovering that they play important roles at other locations in and on the human body. These insights have been revolutionizing how we view the relationship between these commensal organisms and human health.
Gut bacteria promote human well-being by supplying a substantial portion of our vitamin B12 and breaking down complex carbohydrates and other indigestible food components (Ackerman, 2012). While the human genome encodes for a few enzymes needed to process complex carbohydrates, the genome of one commensal bacterium, Bacteroides thetaiotaomicron, contains over 250 such genes. Given that the human genome contains about 20,000 to 25,000 genes and the human microbiome collectively contributes 3.3 million genes, it is hard not to wonder whether we could survive without the enzymes, proteins, hormones, vitamins, and pathogen defenses these organisms provide. As Ackerman (2012) suggests in her opening line: who is controlling whom?
"H. pylori controls appetite; antibiotics disrupt it"
Before the widespread use of antibiotics, nearly 80% of the American population harbored H. pylori in their guts (Ackerman, 2012). Today, less than 6% of children test positive for this bacterium. This decline has been attributed to the increased use of antibiotics to treat minor infections during childhood and the frequent use of C-section deliveries in sterile conditions. In support of the argument that increased antibiotic use is contributing to the obesity epidemic, during the past 30 years the prevalence of overweight or obese adults in the U.S. increased from 30% to 60% (Hurt, Kulisek, Buchanan, and McClave, 2010), which correlates with the increased use of antibiotics to treat minor infections (Ackerman, 2012). There is also some speculation among scientists about whether the human microbiome controls whether tissue stem cells differentiate into muscle, bone, or fat cells; if so, antibiotic use may disrupt this control mechanism and increase the proportion of fat cells produced.
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