If they're anything like ours they'll bind you up big time.
Back in the day I had to live on them for weeks on end. Tinned cheese and bully beef, lots of hard biscuits and sugar packets. The chocolate was hard and had a white coating on it!
If we were on exercise's with the Yanks we'd swap stuff just to make it more interesting. Lots of sugary products in the US ones. That was good because you needed that quick burn fuel. Your GIs loved our "Bully beef".