I would add sugar.
Egg nog is listed on the triangle as away from flour, but it is extremely high in carbs. When I was a kid, I loved egg nog and a couple of years ago I decided to purchase some. I liked it so much I drank the whole half gallon in a day. That night I had horrible painful bloating and looked at the ingredients label to find "sugar", "cane sugar". "corn syrup", and "high fructose corn syrup".
It's not so much that it's high in carbs, it's extraordinarily high in fat. Its main ingredients are egg yolks and heavy cream along with the sugar. What you're describing is like eating an entire cheesecake or drinking a pitcher of melted premium ice cream. The bloating is from the enormous amount of fatty calories that are slow to digest. Not really about the sugar. (And of course it has sugar, it's essentially a dessert drink.)
My money is on the amount of lactose in all that dairy. There's a lot of lactose in a half gallon of nog.
Right? I felt bloated just thinking about drinking a half gallon of nog.
I can barely get through an 8 oz glass of that stuff. Wow.