I have never seen kitedemon give poor advice, so I think the snarkiness is a bit unnecessary.
To the OP - I know you described the rats as "medium", but do you know their actual size (aka weight)? It's already been mentioned, but you should get a digital kitchen scale and weight both him and his rats. Most adult males do not need anything larger than one small rat per week (by small, I mean 50-80g). This is most likely smaller than the 10-15% "rule" that people like to throw out there, but that only really applies to growing hatchlings/juveniles. Just keep him on a weekly schedule and he will gain weight appropriately. If you feed him too much, he will excrete the nutrients instead of using them, and you will basically be wasting food.