No matter how spiritually mature you are, an unhealthy lifestyle and diet will limit your potential.
As a Christian, you are free to eat anything you want. Your diet will not keep you from heaven, but if you continually eat unhealthy foods, you will probably get there much sooner.
All foods are not created equal. In fact, some food should not be labeled "food" but rather "consumable product" or "edible, but void of nourishment."