Jeeze, if that diet doesn't sound idealic, I don't know what is. Personally this time of year and going into fall I am feeding them as much as possible and I want them as fat as possible, usually by Sept. they can't close their shells all the way like you describe, BUT the reason I want to see that is my boxies have to hibernate for 7 months, and really only feed well during June,July,Aug, and sporadically in May and Sept. So when they come out of hibernation they are on the thin side and have no trouble closing their shells all the way, so I thinks it is "healthy" for them to be a little fat in the fall, but the point is that works for my situation, but yours may be totally different, You need to access; do you hibernate? how long? do they get sufficient excercise,ect. to decide what is healthy, and that my vary depending on the time of year, but I think that the consensus "rule of thumb" is that it is not healthy for any animal including humans to stay obeese long term.
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Jeff Benfer
1.0 pastel Python regius
1.1 mojave Python regius
0.1 normal Python regius
1.3 Terrapene carolina thriunguis
2.3 Terrapene carolina carolina
4.1 Kinosternon baurii
1.1 Malaclemys terrapin terrapin
2.2 double het albino and anerythristicThamnophis sirtalis parietalis
1.0 anerythristic Thamnophis sirtalis parietalis
2.2 Iowa snow Thamnophis radix
0.2 het Christmas albino Thamnophis radix
1.1 double het cherry erythristic, albino Thamnophis sirtalis sirtalis
1.1 melanistic Thamnophis sirtalis sirtalis
1.1 triple heterozygous for amelanistic,carmel, and stripe Pantherophis guttatus
0.1 anerythristic motley Pantherophis guttatus
0.1 Okeetee Pantherophis guttatus