At 25 occupants - if they did not load additional stuff into the cabin it was hardly overloaded. Not even with max fuel load.
With 25 Pax + Max Fuel Load = it
will be overloaded
Data from an ATR42-320 :
MTOW = 16900 kgs
Empty Weight = 10900 kgs
Max Fuel = 4500 kgs
There would be approx. 1500 kgs left available for Payload. 25 Pax will weigh more that 1500 kgs
If you prefer "pounds", just multiply the above values by 2.2