Submission and domination

I used to be very fit, and train with weights and as such had a very strict diet.
My poo was always rock hard, and I used to be constipated constantly.
Now I eat crap, and it's the opposite, my poo is like peeing out my bum.
I'd say I poo less now, strangely enough, even though I eat more.

Has nothing to do with fiber - in fact most buffet style foods have barely any fiber. It's all of the salt in the dressing, cheeses, etc. Your weight change is due to water weight. The amount of sodium you're consuming at the buffet is super high. And salt's most pronounced side effect is water retention.

24-36 hrs after the buffet your body sheds all of the water weight.

If you eat 5 pounds of food, you will gain 5 pounds. Then, if you have a 5 pound poop, you will lose the 5 pounds.