Welcome! My name is***** am a 2003 graduate, and currently a Medical Director of a veterinary hospital.
I am sorry to hear about this concern for Ruby.
Yes, that is a concern. For medium to large breed dogs, we do prefer they be lean for joint issues, but your description infers her body condition score is too low.
She is walking a lot, so it could simply be mathematics. She is burning more calories than she is taking in, and therefore, she needs more food. It may be necessary to increase each meal or also add a third mid-day meal.
Second, intestinal parasites. Even if no diarrhea, you must have her fecal test performed.
Bring in a fresh poop sample to the veterinarian. Ideally, within a few hours. Request that it be sent “OUT” to the laboratory instead of being looked at in the hospital (more accurate that way). We are not interested in only worm eggs, but also checking for the very common microscopic bugs like giardia and coccidia. These types of parasites will not be cured with over-the-counter dewormers. Giardia can also be difficult to identify on routine fecal tests, so ask your vet if they always add a “giardia elisa” to the fecal test. Here is more detailed information about fecal testing:Fecal Testing
Also, every 2 weeks, start bringing her to the vet's scale for a body weight check. You must carefully ensure, on the same scale, that her weight is not dropping any further. If dropping, additional testing should include a blood and urine test for an overall health screening and to ensure she is not losing any protein through her kidneys or the gastrointestinal tract.
But, it may be simple math and she is simply burning a lot of calories. Good Luck!
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