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
A bad example is contagious.
Patience and labor will grind everything.
You can't help grief with tears.
With whom you are friends with, from them you will learn.
A holy place is never empty.
Where it is thin, it breaks.
Your own shirt is closer to your body.
There is no smoke without fire.