If adding 1t of fuel for any airplane results in c.g. out of limits, something is seriously wrong. Fuel tanks are usually near the middle of the airplane and (except for trim tanks) fuel load results in limited change to c.g.
Generally you can say yes to the OPs question, unless you hit some other limit. Usually a ZFW limited flight can add fuel upto MTOW (or limited TOW) or Max Fuel Capacity. For a shorter leg MLW might be limiting. In which case reducing ZFW by 1t does allow adding 1t of fuel.