Unexplained Weight loss

I was wondering if anyone has experienced a heavier chin loosing weight on their own without illness? My vet said my chin seems healthy, but she keeps loosing weight. She is a little on the heavier side so it could be a good thing. My concern is why is she loosing weight? There have been no diet changes. She is down to 800g. This time last month (8/13) she was 829g and the month before that (7/9) she was 866g. She has no other symptoms and actually seems to have more energy and bigger poops. Should I bring her to another vet or let her be and just keep an eye on her for other symptoms? Has anymore experienced unexplained weight loss without an underlying illness?

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