Absolutely - you don't lose fat by starving yourself, I can tell you that much.
Cardio on an empty stomach is generally a good method for fat loss - however, all cardio isn't created equal. Empty stomach should be lower intensity/steady state. High intensity cardio like boxing will torch LBM.
To answer the macro question - what are your full stats again?
So you do the boxing and that's it - no weight lifting routine?