Q: I know that fiber keeps you feeling fuller for longer, but I've heard that protein is the best food to stave off hunger because it takes so long for to digest. When fiber keeps you feeling full, is it because it is providing calories for longer than other foods types or is it making your body feel full even though you may be undereating to lose bodyfat.

A: Fiber has two things going for it to keep you sated longer... For one, it does, as you said, take up more room in your digestive tract than heavily processed foods with little fiber. The second reason, which is probably more important, is that fiber actually slows down digestion and insulin release into the bloodstream. Insulin release is what triggers the uptake of the nutrients from the bloodstream into various organs, muscles, and fat deposits. Once the nutrients are gone from the bloodstream you'll start feeling hungry again. So by making the insulin release more gradual fiber keeps you sated longer.

The very important point to this is that you virtually always want insulin release to be slow and gradual! This will minimize uptake of nutrients into fat deposits, thereby keeping you slimmer and leaner. Not to mention helping you avoid type II diabetes. This is why I always always always tell people to eat natural, nutritious, minimally processed foods -- they are the type that will digest slower (in large part because of the natural fiber content) and keep you leaner and healthier.