BASH for loop echo leading zero

BASH for loop echo leading zero

I have a basic number for loop which increments the variable num by 1 over
each iteration...
for (( num=1; num<=5; num++ ))
do
echo $num
done
Which outputs:
1
2
3
4
5
I'm trying to make it produce the output (add leading zero before $num):
01
02
03
04
05
Without doing:
echo 0$num