Is it possible for good food to mess someone's insides up?!?!

My boyfriend is first of all not allergic to anything that we are aware of. He isnt lactose intolerant or vegan or gluten free or diabetic. Generally speaking, he has no concerns when it comes to food.

Now he spent the last 3 years getting divorced and fighting a nasty custody battle. Both he and his ex were young and cooking by the sounds of it wasnt a thing. If it didn't come in a cardboard box and bake for 20 minutes at 400° they were ordering in or picking something up. And when they broke up, he turned solely to take out and fast food.

Literally my boyfriend cannot do more than BBQ a boneless pork chop. And even then I have to marinade it and prep it. And remind him to check the temperature of whatever is on the grill. I love him. But he is not a cook.

I'm big on meal prep and cooking and trying new things.

We have been friends for a while but I really only started cooking for him after we started dating about 5 months ago.

He is always raving about how good a dish is and how he loves this and loves that. But he is always pooping after eating my food. No matter what I make! Chicken. Pasta. Fish. Pizza. Anything I make he has a huge dump. And complains about it.

I'm wondering if his body is just so unfamiliar with real food that he can't process it? Is that possible to have an intolerance to grease free food?? Wondering. I cook all the time and have cooked for lots of other people. And no one else seems to have this issue.