It depends upon your winter.
You're in TX or OK, if I remember right, so I don't think your winters are as bad as mine were in TN.
I think fasting is good for cleaning a dog out and getting a "best weight." It is also good for their health IMO. Wolves and coyotes fast all the time, even in the winter, until they get their next meal.
Also, giving a shank bone really isn't true fasting, because the dogs are eating meat/fat/bone/marrow whilst cleaning their teeth. In fact, they basically spend the whole day eating fat/meat/bone and cleaning their teeth in the process.
Jack