Obesity is widely regarded as one of the most pressing health issues worldwide. The proportion of the world’s population that is defined as obese has risen steadily over recent decades. Can obesity be cured with someone else’s bacteria?
Obesity creates a number of serious health problems including a high risk of developing type II diabetes and a high risk of heart disease. Although the link between obesity and these serious consequences is not completely understood, it involves low grade but chronic inflammation.
Many studies have identified associations between the overall composition of the microbiome and, for example, obesity or insulin resistance (a key precursor step to type II diabetes). The complexity of the gut microbiota and the ethical and logistical difficulties of conducting intervention studies in humans has made it very difficult to identify specific effects of specific bacteria in humans.
A landmark study that went beyond associations to demonstrate direct effects identified differences between the gut microbiomes of identical twins, one of each pair was lean while the other was obese. The use of identical twins removed genetics as a possible cause of this difference. Amazingly, when the gut bacteria from the twins were transferred to bacteria-free mice, those receiving the bugs from obese twins gained far more weight, and put on more fat tissue, than those receiving the lean twins’ bacteria, despite the mice being fed the same diet and consuming very similar amounts of food. This was one of the first demonstrations of a direct effect of the microbiome on obesity, something supported by many studies since then.
Read more here: Ridaura et al. Gut Microbiota from Twins Discordant for Obesity Modulate Metabolism in Mice. Science. 2013. https://doi.org/10.1126/science.1241214