What kind of health side effects would eating once a day have?

I nibble as I can during the day, and eat a "meal" late in the evening as a way to counter the effects of Crohns disease.

I think you would do better to at least try and snack in a healthy manner every few hours.

your digestive system will work on itself if there is nothing else for it to do.

keeping your intestines in peak operating condition is something I would encourage everyone to do. it is no fun when they quit working correctly...

You may also find that you're actually eating too many calories, even though you are only having one meal. You may find that hunger and low blood sugar rob you of some ability to make healthier choices and/or portion control goes out the window.

I'm not a nutritionist but this shouldn't be too much of a problem. Especially if on the other days you are eating a well rounded diet.

On these days where you only eat one meal, what can you consider to be a typical meal? Is it junk food? Lots of veggies? Any real sources of fiber? Etc...?

I think the biggest side effect would be feeling hungry

Body get the energy from food. And it burns a huge quantity of food with in after 12 hours. So your body demands more energy in terms of meal after 12 hours. So have a meal at most 2 times a day.

low metabolism
anorexia and bulimia
electrolyte imbalance that will cause dehydration, muscle spasm, and worst cardiac arrest
potassium deficiency
depression
anxiety
irritability
anger