Sylar doesn’t eat brains

Claire: Aren’t you gonna eat my brain?
Sylar: Claire, That’s disgusting.

Sylar's poking Claire Bear's Brain! Yikes!

Finally, it’s finally clear that Sylar doesnt eat brains but opens it to STUDY it. Using his ability which is “Intuitive Aptitude”, he examines the brain of the ability-bearer to determine how he/she uses or manifest the ability. He alters his own DNA thereafter and is capable of using the ability.