Can breeds vary widely outside the standard?

I have met a few 20lb shih tzus and 15lb pomeranians. Normal?
I also hear about mastiffs and saints and danes reaching 200lbs but is this usually the weight of dogs in the ideal conditions? Or are some of these dogs usually obese? Is it possible for a full grown giant breed to be less then 100lbs and not emaciated?

There used to be a puppy mill in my area that had some amazing animals. They would save for breeding any animal that was not likely to sell. So, if a litter of yorkies had one individual that was extremely large, or a litter of Mastiffs had a tiny individual, they would retain them for breeding. Over the years this created a situation where they were selling puppies (with AKC papers) that were way outside the breed standards.

Eventually, after many complaints to the AKC, they were “sanctioned” by the AKC and could no longer sell puppies with AKC papers. So they formed an alternative organization to provide papers. This was totally legal. Instead of AKC papers people got very real looking certificates from PKC (pet kennel club). Most people buying from them did not realize there was a difference.

A few years ago they went out of business. It got to the point where nobody locally was unaware of their horrible reputation and they couldn’t give a dog away.

All biological systems exhibit variation. This is how “breeds” come about in the first place. Breed standards change over time too. I know that it is not uncommon for purebred dogs to be over or under size for the breed standard and therefor not suitable for showing. In show dogs, it is sort of the point that only certain individuals have all the “perfect” attributes of the breed.

If they didn’t vary from the standards, you wouldn’t need to have standards.