Obesity is a complex problem with many causes: an increasingly sedentary lifestyle, accessibility of cheap and calorie-dense processed foods, long commute times to and from work, recreational leisure pursuits that involve screens and video games. Aside from these factors, though, there is an emerging understanding that our own pursuit of health may have also inadvertently contributed to a propensity towards weight gain. What do I mean? Ironically, advances in medicine and technology that influence bacteria in the gut may actually be making us fatter.
Our understanding of the diverse microbial atmosphere of the digestive system (termed the microbiome) has lead us to recognize how critical gut bacteria are for health. For example, our gut houses over 100 trillion microbial cells that “influence human physiology, metabolism, nutrition and immune function.” Not convinced? Check out this NPR video illustrating the human microbiome, courtesy of artist Ben Arthur:
The importance of the gut microbiome in obesity was recently established by transplanting fecal microbiotic organisms from adult female twins discordant for obesity (i.e., one twin was obese, the other wasn’t) into germ-free mice. The mice given the bacteria from the obese twin exhibited increases in body weight and detrimental metabolic changes. Consequently, one hypothesis is that many of our scientific, technological and medical improvements have introduced larger quantities of antibotics, toxic environmental agents and processed foods into our diet, altering our gut microbiome for the worse and predisposing us to obesity. In other words, certain lifestyle and medical practices, as well as exposure to bacteria through infection and disease, may alter the balance between bacteria that contribute to obesity and those that prevent it.
So what can we do about our bacterial dilemma? Diet is the obvious fix for digestive malaise, but again evidence is somewhat inconclusive. As a recent NPR article details, eating a large volume of fiber-rich foods, whole grains and naturally-occurring probiotics (live microorganisms that improve gut bacteria) may be beneficial. Michael Pollan has written compellingly in the NY Times that fiber-rich foods, particularly those grown organically in soil that promotes the propogation of healthy bacteria, augment the fermentation of bacteria in the large intestine that stimulates microbial growth. However, evidence is lacking about how much and what types of foods can definitively influence the human microbiome, particularly when it comes to foods now supplemented with probiotics, such as yogurt. And finally, evidence supports that establishing an individual’s gut microbiome starts from the mother at birth … apparently just another thing we can blame on our mothers.