Why Eddie had body issues after recording his lines for Early Man?

"...So Maisie and I got dressed up as cave people, with huge spears, and started 

fighting it out. And that was how I got into character.... " - VIDEO

Eddie Redmayne at the World premiere of Early Man on 14 January 2018

Maisie Williams and Eddie Redmayne recording their lines 
at Aardman Studios with director Nick Park
 They are not dressed as cavemen, but look at them!

My gifs from the premiere video here

In the  interview below Eddie is talking about Nick Park, the characters, the amazing
cast and he reveals some other behind the scenes details about the recordings.

"From my parents to my grandparents - my grandma is hugely excited about this
film - down to my nieces, nephews and godchildren. There's something in it,
that is so on and so uncynical, it's just so damn funny."

 my screenshots