If indeed overeating is the cause I would suggest the homeopathic remedy Nux Vomica 30c potency. One or two doses should correct the issue. It can rapidly relieve the discomfort and diarrhea caused by a change in diet, overeating or the food being too rich. I recently attended a holistic veterinary workshop. The veterinarian used, 'Pet Remedy Charts' to teach the class. They are awesome! They make charts for Homeopathy, Herbal Medicine, Flower Remedies and Acupressure as well. They give you remedy suggestions and and exactly how to dose them for every condition you can imagine. Their better than books, I use them all the time and carry them with me where ever I go. They make them for dogs, cats, horses or birds. Their not expensive. I got mine online at petremedycharts .com I live in the US so I'm not sure if they ship internationally or not but it would be worth finding out.