Сытой мышке и сало не вкусно

When a man is not hungry, he is hard to please

Var.: Мышь сыта - мука горька. Сытая мышь и муки не ест

Cf: Plenty makes daintiness (Am.). Plenty makes dainty (Am., Br.). То him that lost his taste sweet is sour (Br.). Too much plenty makes mouths dainty (Am.). When the cat is full, then the milk tastes sour (Am.)