How to incorporate the body field back into a content type from which it has been previously deleted?
In a hook_update_n(), module_install(), module_enable(), or devel module eval php code:

$types = node_type_get_types();
node_add_body_field($types['my_content_type_name']);


giving it the machine name of your content type, and optionally you may provide a label for what you want the human readable label for the field to be (defaults to 'Body'). see node_add_body_field() API documentation