Just enough, every time.
Every meal, measured to the gram.
It's easy to love a pet with an extra handful. The bowl gets topped up when they ask, the scoop runs a little fuller when they're watching, and slowly the weight comes on without anyone quite noticing. Weighing each meal takes the guesswork out of it - the same considered amount, morning and night, so they eat what they need rather than what they can talk you into. It's a small habit, quietly kept, that looks after them in the long run.