Nuclear Fusion and Fission
Note that binding energy of nucleons does not mean contained energy, but the energy needed to break it. 

Therefore kernels with lower binding energy per nucleon contain more nuclear energy per nucleon and have higher mass per nucleon.

It means forming kernels with higher binding energy per nucleon releases energy and vice versa.

It is the same as for chemical bonds, just some 6-7 orders higher.

E.g. nitroglycerine has lower binding energy per atom than reaction products formed by its explosion.