I apologize in advance for the length of this post but there’s a tremendous amount of valuable information and answers on this site as well as links to many others so I collected some relevant links from posts in earlier threads to see if I could help to answer your questions. For someone who is pre-diabetic, like myself, as well as for Type I or II diabetics, dietary control of blood sugar levels to as close as normal is always desirable. Together with exercise and meds, if required, it can go a long way to delaying the onset of complications, reducing the severity of the complications and now the latest clinical evidence proves, unequivocally, that diet and exercise can reverse prediabetes and the painful PN associated with it in some cases.
As for a typical diet the ADA or American Heart Association diets are good places to start and you’ll find many good suggestions from forum members along with recipes too. For myself, I try to eat a lot of fresh fruits, vegetables, whole grain breads, whole wheat pasta, lean cuts of beef in moderation, fish, skinless chicken and turkey, pork and stay away from fatty foods, cookies, cakes, candies, most of the normal “snacks” etc.

Here’s one of the early studies to suggest a link between impaired glucose metabolism (prediabetes) and idiopathic painful PN and the authors were among the first to advocate the importance of an OGTT (oral glucose tolerance test) in the diagnoses.
http://www.jabfm.org/cgi/reprint/17/2/127.pdf

I “lifted” several links from earlier threads to excellent articles about improving and even reversing PN from prediabetes.
http://appneurology.com/showArticle....leId=188500771

http://care.diabetesjournals.org/cgi...ract/29/6/1294

http://www.sciencedirect.com/science...d469fd5964375c

http://www.neurologyreviews.com/may06/neuropathy.html

I think the info below which is a direct quote from Smith and Singleton’s study is the best summary I’ve read to date. Their work showed that there were measurable increases both in small nerve fiber densities and length based on comparison of the 3mm distal (ankle) and proximal (thigh) skin punch biopsies after 1 year in the study. All patients experienced improvement and/or reduction in pain except for those people who had the most severe damage at the outset.

“In the present trial, the investigators performed 3-mm skin biopsies at the distal leg and proximal thigh, at baseline and after one year. Baseline distal IENF density averaged 0.9 fibers/mm, and proximal IENF density averaged 4.8 fibers/mm. After one year, distal IENF density had improved by an average of 0.3 mm, and proximal IENF density had improved by an average of 1.4 mm. The improvements were significant.
“By the study's end, the IENFD (intraepidermal nerve fiber density) had increased by about a third for all patients except those with the worst loss of nerve fibers in their extremities. The improvement in proximal IENFD correlated with decreased neuropathic pain and a change in sural sensory amplitude. "Over the first year of follow-up, IGTN (impaired glucose tolerance neuropathy) subjects lost an average of 4% of their body weight and increased exercise from less than 15 minutes to more than 80 minutes per week," said Singleton.
In a press briefing at the AAN meeting, Smith noted that the findings indicate that the effects of IGTN (impaired glucose tolerance neuropathy) may be reversible. In correspondence with Applied Neurology, Singleton echoed Smith's view, commenting that the findings "are of great clinical significance, because the neurology community regards length-dependent neuropathy in general and diabetic neuropathy in particular as irreversible and progressive. The data underscore the importance of identifying neuropathy patients very early in the course of their disease."

With regard to the pain, I’ve read that the pain may actually worsen initially as damaged nerve fibers regenerate and new fibers are produced but eventually the levels do lessen.
Overall, the studies show that in the patient populations examined that DIET and EXERCISE not only improved glucose control and reduced weight, LDL cholesterol and triglyceride levels but that it improved small fiber function, increased intraepidermal nerve fiber density and improved neuropathic pain severity. I think that there is some reason to be hopeful even if the PN is idiopathic and not directly linked to prediabetes.
Hope this very long post helps a little.

Alkymst