Despite popular perceptions, there is consensus amongst the world’s major diabetes associations (e.g., American Diabetes Association; Canadian Diabetes Association and Diabetes UK) that 1) sugar does not cause diabetes and 2) that sugar free diets should not be recommended to people living with diabetes. The reasons why are simple:
1) There is evidence from systematic reviews of randomized controlled trials that the best way to reduce the risk of developing type 2 diabetes is to consume 2,000-2,500 less kilojoules each day by eating less fat, and in particular to reduce the intake of saturated fat and increase the intake of dietary fibre. Of course, some people may also reduce their kilojoule intake by reducing the amount of added sugars that they consume.
Data from observational studies suggest that excessive consumption of sugar sweetened beverages (≥ 1-2, 355 mL drinks a day) is associated with an increased risk of developing type 2 diabetes. Perhaps surprisingly, there is also evidence linking non-nutritively sweetened ("diet") soft drinks with the development of type 2 diabetes. Unlike randomised controlled trials, observational studies do not prove causality and consequently, more research is needed to determine if these suspected links are real. It could be that people usually drink regular or diet soft drinks with other highly processed foods (crisps, chips (French fries), savoury snacks, pastries, etc...), or alcohol, and that its the overall dietary pattern of highly refined carbohydrate consumption that's really to blame.
2) Sugars, oligosaccharides and starches are digested, absorbed and metabolised to the sugar glucose. Therefore people with diabetes need to carefully balance the type and amounts of sugars, oligosaccharides and starches that they eat and drink each day to ensure their blood glucose levels do not go too high or too low. The International Diabetes Federation recommends people with diabetes use the glycemic index for assessing the type of carbohydrate they consume. Information about the total amount of carbohydrate in a food is available on food labels.