The higher up in your GI tract the obstruction is (closer to your stomach), the quicker and more severe the symptoms will be. That is because when things get backed up to the stomach, nausea and vomiting occur more quickly and there is more pain. If the obstruction is near the pouch, then it takes longer for things to develop to the point of affecting the stomach.
If it is a complete obstruction, as opposed to a partial obstruction, symptoms develop more quickly too. You should gauge your worry based on the degree of pain and other symptoms. If pain is severe or you are vomiting, it could be serious and require emergency surgery. So, you should never worry about over reacting and ER docs will err on the side of caution and check for a twisted bowel, blood clot, hernia, etc.
Also, just a reminder: food seldom has anything to do with an obstruction unless you have a very narrow stricture (as you'd find with Crohn's). Of course, you should not be wolfing down food without chewing!
Jan