I have been in the industry for years. THC is the active ingredient that causes an increase in appetite. However, there's another known chemical called CBD which is non-psychoactive. Many breeders have isolated this chemical through cross breeding and if you're lucky, you can find this amazing strain, get medicated, and not get "high." It decreases the chance of the "munchies" too.
However, to recommend marijuana as an aide with diabetes it should really ought to be looked at as a dietary supplement. Raw cannabis juicing has INCREDIBLE anti-inflammatory properties and has healed things like fibromyalgia and cancer.