This is part 2 of a multi-part blog discussing Do Calories Matter. If you have not read part 1, here is the link. HTTP://WWW.LOUDHOUSECROSSFIT.COM/DO-CALORIES-MATTER
Now let’s talk about our gut health.
Bear with me a bit here, this will be a little “sciency”. Gut flora or, more appropriately, gut microbiota, consists of a complex of microorganism species that live in the digestive tracts of animals and is the largest reservoir of microorganisms mutual to humans. In this context gut is synonymous with intestinal, and flora with microbiota and microflora.
Gut microorganisms benefit the host, aka you, by gleaning the energy from the fermentation of undigested carbohydrates and the subsequent absorption of short-chain fatty acids. The most important of these fatty acids are butyrates, metabolized by the colonic epithelium; propionates by the liver; and acetates by the muscle tissue. Intestinal bacteria also play a role in synthesizing vitamin B and vitamin K as well as metabolizing bile acids, sterols and xenobiotics. 
Your gut is home to over 100 trillion bacteria. (Bugs) In fact, 10 times more bacteria than human cells. So why is this important? The health of your gut flora has a direct impact on your overall health and recent studies have shown that it could also affect whether or not the host, aka you, are obese or not.  “The accumulating evidence strongly suggests that the gut microbiota play an important role in the regulation of energy balance and weight in animals and humans and may influence the development and progression of obesity and other metabolic disorders, including type 2 diabetes. Although not a substitute for diet and exercise, manipulation of the gut microbiome represents a novel approach to treating obesity.” While there needs to be more research in this area to determine what a “true” healthy gut microbiome looks like, the evidence is certainly adding up to show that it can have a giant impact, not only on your overall health, but also in treating obesity.
In part 3 of this post, I will discuss what to eat and why… stay tuned. http://en.wikipedia.org/wiki/Gut_flora