Yep, at one point in my life I was consistently cycling for 30 hours a week and eating enough became a chore. So it's definitely possible, but it requires enough exercise that's essentially a full time job.

I had a similar situation in my early 20s.

My conclusion was that past a certain point you need to use liquid sugar (soda especially) to get your body to put on weight past a certain point.

Even with absurd amounts of fat, carbs and proteins I could not process enough food to put on the weight I wanted too. Sugar is the backbone of massive weight gain.

I once trained pretty hard for several months for a martial arts competition. I upped my calorie intake to keep up with the training and put on about ~15lb of muscle. What people don't tell you about this sort of intensive training is just much extra time you spend each week shopping, cooking, eating and taking a shit - on top of all the training!