With accent marks:
Сы́тый голо́дного не разуме́ет.
A well-fed man does not understand a starving one.
A well-fed, prosperous person does not want (and often is not able) to understand what it is like to be hungry.
The old Russian word "разуметь" in this case means "understand".
Other Russian proverbs
In a quiet whirlpool, demons live.
You see your friends in the times of trouble.
Where it is thin, it breaks.
Bitter truth is better than sweet lies.
Don't go to the woods if afraid of wolves.
Put your trust in God, but don't make mistakes yourself
Оne can not see the wood for the trees.
If I knew where I would fall, I would lay some straw there.