Disable lazy loading ?

Hi,

I have 2 active records with has_one/belongs_to association between
them.

class Story < ActiveRecord::Base
  belongs_to :conclusion
end

class Conclusion < ActiveRecord::Base
  has_one :story
end

Sometimes I fetch a conclusion with story in eager loading, sometimes
I don't fetch the associated story.

I want to know when the associated story is fetched or not
conclusion.story.loaded? doesn't work.

Another question : how to completely disable lazy loading ? In order
to be able ton simply do : conclusion.story == nil.

Thanks for your answers.