Food plays a major role in Jewish life. Imagine a wedding or bar mitzvah without food. It would be like a pub with no alcohol. What would be the point? For a culture that is so focused on food, then, it makes sense to have many rules that govern our eating. Without doubt, the primary reason for the kosher laws is spiritual health. You are what you eat - and who wants to be a pig?
Yet there is another very important reason for keeping kosher: self-control.
I once attended a weeklong course on macrobiotic eating. It is a very healthy, but incredibly restrictive diet. My wife and I were on the course with about ten other couples, all of whom were not Jewish. We found it very interesting how much easier it was for us to adapt to this new way of eating than everyone else. It was because of our kosher laws. We were already used to controlling ourselves in the area of food consumption and this diet was merely an extension of that. For those, however, who had no experience of long-term control in eating, it was a much harder adjustment.
In Jewish thinking, much of life is about self-control. The more we take control of ourselves, the more we can direct ourselves toward meaningful accomplishment. And conversely, the more we allow our desires and passions to rule the roost, the less we are able to achieve. Food is a big area of desire and needs serious control. Because every animal, the human included, needs food for survival, it can drive our desires crazy. Every wife knows that keeping her husband well fed will make her life a heck of a lot easier. Eating is an area that calls for great self-control, to ensure that we don't get carried away.
So the Torah gives us laws to help create boundaries and self-control. But a certain amount is still left to us. Healthy foods don't taste so good. Unhealthy foods are very attractive. We need to make our own boundaries, too.
Ultimately, though, food is one of the simpler challenges in life. If we can't overcome our desires in this area, we will be seriously challenged in the more significant areas. Keeping kosher teaches us to take control, not just in the spiritual aspects of food, but to extend our control to the practical, health aspects - and from there to the areas of life that really matter.