I've been looking through a number of papers linking the microflora in the gut with obesity. It is an interesting line of research. The idea is that an imbalance in the different types of bacteria predispose a person to gaining weight.
In this paper, it is proposed that obesity is actually an extension of the "hygiene hypothesis". Just as conditions can be too sanitary and not allow the immune system to properly develop, in these conditions the gut microflora become unbalanced as well. They state that imbalances in the gut actually precede the overweight condition.
The treatment for this would be prebiotics and probiotics, or plenty of fruits and vegetables. Fermented foods would also have an impact. I'm sure more studies on this are in the works.
