Animal welfare charity the Scottish SPCA said Stacey Moran, 27, from Coatbridge, North Lanarkshire, admitted failing to feed and provide vet care for her cross-breed Sasha.
The dog had been shut in a dirty room and was around 2.5kg underweight when found.
The Scottish SPCA was alerted by the local housing department following concerns that animals had been abandoned inside Moran's home.
Inspector Sam MacDonald said: "There was no food or water available for her and she was extremely underweight, with her spine and ribs easy to feel through her long, fluffy coat.
"I immediately took Sasha to a vet for examination and she was found to weigh only 4.5kg, when a dog of her size should be around 7kg.
"Shockingly, the vet found evidence that Sasha had been eating her own faeces, which demonstrates how desperately hungry she was.
"Moran stated that she had been on holiday for three days and that a family member had been left responsible for feeding her dog, but it was clear that Sasha's condition had developed over a much longer period of time.
"Thankfully, Sasha made a full recovery in our care, gaining 2.35kg through simple, adequate feeding and we were delighted to find her a loving new home with a responsible owner.
"We are pleased Moran received a 20-year ban for the suffering she caused Sasha. She gave no reasonable explanation for Sasha's condition and therefore we considered this to be a case of gross neglect."
Moran was sentenced at Airdrie Sheriff Court yesterday after pleading guilty to causing unnecessary suffering to her dog under the Animal Health and Welfare (Scotland) Act 2006.