The body has a lot less muscle and a lot more organs. The crab's lungs appear as feathery cones lining the side of the body. They're pretty fibrous and not good eats.
There's some greenish stuff, which is the liver, called the tomalley. You can eat it. Some love this part of the crab.
If you have a female crab and you see bright orange stuff inside, that is edible. It's the roe or eggs.
So, there's some good meat in the body of most crabs, but it is located in cartilage-lined channels. So, depending on variety of crab, it can be more work for chunks that are smaller than you'd get from the legs.