NEW YORK (AP)—Novak Djokovic attributes his success in recent years to a change of diet. Now he'll be sharing his nutrition tips in a book to be released before the U.S. Open.

"Serve to Win" is the title of Djokovic's "nutrition-based performance guide" that is to be published next month.

The top-ranked Serbian has won five of his six Grand Slam tournament championships since adopting a "performance-focused" gluten-free diet in late 2010. In 2011, he took the Australian Open, Wimbledon and the U.S. Open. He has since won two more Australian Opens.

Djokovic says "finding the right foods for my body has made me lighter, healthier, and more focused." He adds that "it's made all the difference in my career and in my life."

The book will be published by Ballantine Bantam Dell, part of Random House.