Is it important to eat all these new "pro-biotic" foods? What are they anyway?

First off, "pro-biotic" foods are foods that contain populations of live and active beneficial bacteria.  Your digestive system is filled with symbiotic bacteria that eat what you eat, and also help you to digest certain foods. These beneficial bacteria also provide population control to guard against harmful bacteria taking over (less room for pathogenic bacteria to multiply and expand). This is a really hot topic of research among the obesity and nutrition scientific community. The types of bacteria in your digestive system have been found to differ between normal weight (lean) and obese people, and by changing the type of bacteria that rats are exposed to, scientists can cause some rats to gain more weight than others.  Some people speculate that the bacteria alter the way we metabolize and absorb food.  However, it is not clear yet whether obesity causes differences in beneficial bacteria, or whether the changes in bacteria contribute to obesity (the classic which came first - chicken or egg?).  However, the types of bacteria in your gut are likely to be contributing factors in our battle against obesity, not a magic bullet.  Also, physicians and nutrition counselors have found that people with digestive problems, such as irritable bowel syndrome (IBS), Crohn's disease, Celiac disease, and others can reduce digestive problems by adding more pro-biotic foods to their diet. There are a myriad of pro-biotic foods on the market, including cereals, drinks, and yogurts.  If you have digestive problems or are trying to lose a couple pounds, you might consider trying some.  There's no need to go crazy though - a little bacteria go a long way!