I've been on a meat sabbatical recently over lent and I've gone forty days without meat. Before my break I was a pretty keen carnivore, and now that I've started eating meat again I've been having slight stomach pains. They might just be the kind you normally get, but can reintroducing something like meat into your diet upset your innards?
closed as off topic by Moses, VPeric, Ivo Flipse♦ Apr 16 '12 at 8:25
Questions on Physical Fitness Stack Exchange are expected to relate to physical fitness within the scope defined in the FAQ. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about closed questions here.
I've seen this a lot in my friends who've gone periods of being vegetarians, and also experienced this first hand as someone who's been a vegetarian for a full year before going back to being an omnivore.
The stomach distress you're feeling is quite normal, and may be just as much psychological as it is physiological. While the psychological response depends largely on what your mindset is towards meat and why you chose to reject it for four weeks, it can be just as tangible as the physiological response.
From the psychological perspective, being a vegetarian trains you to dislike meat (YMMV), and when you start eating meat again you will have to overcome that mental roadblock that meat === bad. Even having a placebo that you believe to be meat can result in your body rejecting it with stomach aches or even vomiting. Even the taste or texture of meat can be enough to trigger a psychological response.
From the physiological perspective, being a vegetarian for a prolonged period of time will result in your body not being accustomed to the process of digesting meats. It's not like you lost the ability to digest meats, you just have to give your body time to re-acclimate to the whole process. I'm not quite sure how long of a period it takes for someone's body to "forget" how to digest meat, but I've seen it happen to people in as few as two to three weeks of being vegetarian.
My suggestion is to gradually re-introduce quality meats back into your diet so your body has time to re-adjust to that whole animal fat digesting thing. What do I mean by quality? Well, anything that is not fast-food, since most fast-food burgers can barely qualify as meat in the first. Stomach distress is normal for people in your situation, and as long as you don't overdo it (save the hot-dog eating competition for later, okay?), you should be fine.
Based on what you mentioned:
I assume by saying carnivore it means that most of your food intake came from meat. Going with this assumption, i do not believe your stomach pain is caused by meat.
What probably happened is that during lent, as you stopped eating meat (and maybe other food types), you actually decreased your overall food intake ,which in its majority consisted of meat. So, this means you were eating much less quantities of food , and the stomach is an elastic organ : the more you eat, the more it gets dilated , and vice versa. So your stomach actually shrink during lent.
Thus after 40 days of eating less, your stomach got used to small quantities, and that's why now that you are having meat again , ie eating more quantity , your stomach is getting dilated again beyond the limit it reached during lent, and thus you feel the pain.