Mass defect of nuclear fission/fusion (1 Viewer)

[Bob99]

I am a bit confused about the mass defect occurring from nuclear fission/fusion reactions. Online sources + textbooks say that the products of a nuclear fusion reaction will have less mass than the reactants, and will release energy in relation to E=mc^2. But in my matrix book, they are saying the opposite and that the product of nuclear fusion will be heavier, and that energy has to be put into the reaction instead of the reaction releasing it. So yeah can someone please help me with this and clear my doubts.
Thanks.