A cram ration is lighter but less filling than a food ration; their nutrition/weight ratio is the same.
Eating a cram ration gives the message "This cram ration is bland".
Encyclopedia entry Edit
If you want to know what cram is, I can only say that I don't
know the recipe; but it is biscuitish, keeps good indefinitely,
is supposed to be sustaining, and is certainly not entertaining,
being in fact very uninteresting except as a
chewing exercise. It was made by the Lake-men for long journeys.