My older brother has a leopard gecko named Spike, at least 8-10 years old, and was in good health for the last few years I've known her. She was getting about 20 crickets every 2 weeks, and water every few days (or weeks, depending on if brother paid attention). Even with this extremely poor diet regimen somehow she managed to keep up good fat reserves in her tail and had fairly good activity levels despite being a little small and skinny through her limbs. Her weight has dropped in the last month, though, and she's gotten extremely lethargic; she has no more fat reserves left and is basically skin and bones. Poor thing!
(PS, I don't live there and am not able to see to her myself day to day.)
My family needs to know what they should do for her. I've never had to care for an emaciated lizard before, so I'm not sure how much/often to feed her. Even with the heightened weakness and lack of energy, Spike will eat a lot of crickets if a lot are placed in her cage, as she is used to. But if offered 3-4 she will maybe eat one or two and the rest will remain until we take them out. Why this odd feeding behavior, and what are the proper steps to take to get her back up to speed?