When you eat you probably think you're feeding your body, all 10 trillion cells of it, and you'd be correct. However you're also feeding your gut flora, all 100 trillion of them - yes that's right 100 trillion!
Our cells are outnumbered by the micro-organisms that live in our gut and they all like to eat - so when you're eating you're not just providing nutrients to your cells, but you are also feeding this huge population living inside you!
Given their volume you shouldn't be surprised to here that they have a huge impact on our health mainly through modulating our immune response (being a major influence in allergies and immune over-response), but they also effect how will we digest and absorb our food and even affect our appetite.
So what do they like to eat? Well that depends on the type (there are 2000 different types) but as an acceptable generalisation: those that are more problematic for health like to eat sugars and refined carbohydrates, a big mac with a chocolate milkshake suits them just fine, whilst those that are more beneficial have healthier tastes. Their favourite foods are vegetables, and second to that they like lower sugar fruits such as orchard fruits and berries.
The more you feed the unfriendly type the more they flourish and the less room there is for their healthy cousins to grow. So when you're putting food into your mouth don't just think about what you fancy eating, but also think about the 100trillion micro-organisms you'll be sharing your dinner with and what might be good for them!