The American Society for Microbiology invited Dr. Martin Blaser, the director of the Human Microbiome Program at New York University, to speak about the rise of disorders like asthma, juvenile diabetes and obesity, and how that might be related to changes in the microbiome, topics addressed in his book "Missing Microbes: How the Overuse of Antibiotics is Fueling Our Modern Plagues."
Blaser's laboratory has been researching how bacteria influences human health and specifically, how the microbiome plays a role in the development of diseases. His lecture, presented in this video, is about 40 minutes long (it's worth it just to click through if you don't have time for the whole talk) and it delves deeply into this question and what his research has found. One finding for example, is that disruption to the microbiome early on in life, such as through antibiotic treatment or delivery by caesarean section, is correlated with weight gain.