No, starving will only cause a bigger insulin spike with meals because then every meal occurs after a fast, which is worse.  Some vets recommend down to 1% of body weight but if they don't need to lose weight it is pointless at best, and possibly harmful to cut calories so extremely.  I don't think Mouse needs to loose weight from your photos. 

I've list track if why you're not using Metformin but I assume it wasn't working?  If not, I think you should look into putting them on Canagliflozin/Invocana then.  Ask your vet to email drkellon at gmail dot com to get the bloodwork and management protocols.  You can do a Message search for Canagliflozin or Invokana and Ertugliflozin or Stelgatro, or search "flozin" to learn more about what is involved.

--
Kirsten and Shaku (IR + PPID) - 2019
Kitimat, BC, Canada
ECIR Group Moderator
Shaku's Case History
Shaku's Photo Album