At what age does an average White German Shepherd become an adult?

I have a male, White German Shepherd. He just turned 13 months. I've found mixed answers, from 14 months to 3 years. Is there any sign in behavior or anything I should be looking for? I've heard they usually get less active and don't eat as much. I also still have him on puppy food... when should I switch that over to adult?

Large breeds are their 'adult' size by 1.5 to 2 years. There aren't really any signs of adulthood, but in terms of puppy or adult food, dogs are typically considered 'adult' at about a year old.

77-85 lbs at adult hood.

German Shepherds usually reach physical maturity at about 2 years olds, this depends on bloodlines and even what kind of food is fed. Mental maturity is another matter. Most reach it between 2 and 3 years, again, depending on bloodlines. My GSD didn't mature mentally until he was about 3, and physically about 2 1/2, but my female was mature both ways by 2. It's just different for every dog, just like people. There are no big signs marking maturity, just subtle ones. They may react a little differently to certain situations, maybe be a little more protective or alert around the house.As for activity, they usually get less active because they have learned how to behave properly!I usually change my dogs over to adult food at around a year. You can generally tell when it's time for a change when the food you feed isn't enough anymore. By this I mean, they may be too skinny or fat even though you haven't changed the amount you feed. Change in coat texture is also a sign, is it dull? dry? then it's probably time for a different food.Hope this helps. Good luck.