The game crashed whilst initializing game Error: java.lang.OutOfMemoryError: Java heap space

Whenever I click the play button in the Minecraft launcher, the launcher closes, and it reopens shortly after with the message: 

The game crashed whilst initializing game
Error: java.lang.OutOfMemoryError: Java heap space

 

I have already tried allocating more RAM and I made sure that I'm on a 64 bit OS running 64 bit Java. What should I try? I have attached my crash report.