Thank you for your reply. Twinkle has not put on any wait in fact she seems quite thin. I have only looked after for a few days on two occasion while my granddaughter was away. She has a sister living in a separate cage. The sister has grown a little larger, and prefers eating "herb hay" and not too many of the concentrated pellets they both have. And she drinks very little in comparison. Twinkle hardly touches the Hay but consumes an enormous number of pellets. Does this give you a further idea? Should my granddaughter feed her the hay and remove or restrict the pellets for a while to see if this helps? Do you recommend any particular hay? For how long should Amy try this with her before consulting a Vet please?