If you bulk up from 150 pounds to 200 pounds and you maintain your ability to do 20 pull ups, it means you added STRENGTH and QUALITY WEIGHT to your frame.
You are essentially doing 4000 pounds of work (20 reps x 200 pounds bodyweight) in a set of 20 chin ups instead of 3000 pounds (20 reps x 150 pounds bodyweight).
Now imagine if you go from 150 pounds to 200 pounds but your pull up max drops from 20 to 5.
Your body mass increased but you most likely didn’t improve your body-composition.
This is why it’s important to start off your training career with mastering basic bodyweight exercises… and then include them in all your programs later on.
Being skinny-fat, you have a very easy time gaining body-fat when you bulk up.
By always maintaining your strength on bodyweight exercises, you ensure that you see positive body-composition changes during your bulk.
Be proud but stay hungry!
Oskar Faarkrog, ISSA Certified Trainer