Can I change my puppy's future weight? Diet

I ordered a Caucasian Ovcharka puppy, I have had a strong love for this breed for many years.I was thinking that the puppy will grow into a dog with about 154 lbs weight but after we paid the puppy's money, our veterinarian predicted that he will be around 176-198 lbs when he becomes an adult.

Is this an unchangeable prediction or can I reduce/affect his future weight through adjusting his food?

Starving or overfeeding always affects, but neither is good for a dog

Thanks for your answer. How does my veterinarian predict his future weight, by looking at puppy's current weight or considering his parents' weight?

He probably uses one of the online apps that forecast based on the puppy's weight at any given age. They are a guide but the results are not set in stone, and are bound to be more accurate with a popular breed than a comparatively rare one. Have you asked the breeder for her prediction? Breeders usually know which of their puppies will make the largest adults.

Thanks for your answer.