from the websites www.howto.tv and http SIZE REALLY DOES MATTER How to tell if your cat is overweight using the Purina Body Condition Tool It is estimated that a third of cats and dogs in the UK are overweight. To help you understand whether your cat is overweight, underweight or just right, PURINA has created a range of free, easy-to-use tools, tips and advice accessible on www.purina.co.uk/sizematters. Vet Zara Boland demonstrates how to use the Body Condition Tool on your cat in this . Cat Health.