I underwent pre-diabetes training 18 months ago. Apart from eating predominantly natural, unprocessed food without additives, the most useful advice was to keep carbohydrate portions between 10 to 14 per day (a portion contains 10g of carbohydrate).
Eating low glycaemic foods helps too.
I've also looked at the DoH healthy eating guidelines, and found the evidence underpinning it wanting, to say the least. The above measures are beneficial to health, whereas the recommendation to restrict saturated fats seems to be based of flawed observational studies.
What does everyone else think?