reas a file partially line by line

I need to read a file fron nth to n+m line by line using bash

ie
while read line
do
# soem stuff
done <<file

But The file is so big I am only intersted in reading ceratin portion of the file ie from nth line to mth line where m is alwasy greatr than n

sed '8,12!d' file | while read line
do
# some stuff with lines between 8 and 12
done

Thank you!