How old are Leos when there tails start to fatten up? Ive got a vet appointment in 2 days for my baby boy because he dont seem to be gaining any weight. I just want him checked out and make sure there are no parasites or other issues. I bought him at my local pet store. There a family run business and know there breeders well. Ive gotten my bearded dragon and my african fat tailed gecko from them too with no issues but this little leo is worrying me.