You can eat whatever you want if you just work out seriously an hour a day. If you do that properly, gaining weight will become the challenge.
(Exercise is still extremely good for you though!! Highly recommend!!!)
Many people appear to experience a commensurate increase in appetite after exercise such that they do not lose weight unless they also consciously restrict calories.
Resistance training (bouldering for me) seems to have little effect one way or the other.
If I'm doing High intensity interval training (usually stair sprints) on a regular basis, it's hard to eat enough, my metabolism gets absolutely jacked.
One jar of peanut butter is 3000 calories alone.