Does pre-populated body for content types in Drupal 7 affect performance too? From highest rated answer of this post (Drupal 6 case):
Does having too many content types negatively affect site speed and performance?

It is said that:


  Sharing fields among the content types does affect the performance.


But when creating new content type in Drupal 7, the body field will be pre-populated. When many content types created, if not deleted, this field will be shared among all content types.

This is the body field as seen in admin/reports/fields:


The question is, does it affect performance? and what is the best to do for performance? Do I need to delete the pre-populated body?
tl;dr: No.

What happened in D6 when you shared a field, was that it got moved to it's own table.
This became irrelevant with D7, as all fields are now stored in separate tables, which was a very controversial decision, due to the performance effects this has.

If you want to increase performance, you can read some more here: How do you improve drupal performance.