This is referring to building muscle. You can still maintain good GH levels by following his guides. But he mostly talks about building your body so having a meal or shake after your workout will preserve your muscles best.
DON'T WASTE YOUR MONEY ON INTERNET HEIGHT SCAMS - 99% OF THEM DON'T WORK - - YOGA STYLE STRETCHING, KICKING, HANGING & EXERCISES ARE THE ONLY WAY TO INCREASE YOUR HEIGHT IF YOU ARE AN ADULT (OR RISKY, EXPENSIVE SURGERY!) WE'VE RESEARCHED EVERYTHING AND CAN TELL YOU WHAT'S A SCAM AND WHAT IS WORTH CONSIDERING. IF THESE SO CALLED "MIRACLE" PRODUCTS ADVERTISED BY THESE INTERNET COMPANIES WORKED, THEY WOULD BE ON BILLBOARDS, TELEVISION AND THE RADIO AND WOULD BE KNOWN WORLDWIDE!!!!!