It seems to me that the author is mixing up Type I and Type II diabetes. Type I diabetes is an autoimmune disease which usually has a juvenile onset. If it were to go untreated or very poorly managed over a long period of time, it could certainly cause kidney failure by 27. (Although DKA and a diabetic coma is more likely to lead to death if the management is that bad.) TYPE 1 DIABETES IS NOT CAUSED BY DIET, LACK OF EXERCISE, OR ANYTHING ELSE BEYOND GENETICS!!!!! Type I is managed by taking insulin. Type I diabetics can pretty much eat whatever they want without risking their health, as long as they take the right amount of insulin and manage their blood sugar closely. Some foods make it easier than others.
Type II diabetes is rarely diagnosed in juveniles, and onset is most common around age 45. Poorly managed T2 can lead to organ failure as well. It's caused by diet and being overweight, among many, many other factors that are not completely understood. It's exceedingly unlikely that someone would have had T2 long enough to have kidney failure at age 27. Diet and avoiding high-sugar foods is an important factor in manging T2.
In short: Type 1 is what kids/young adults usually have and it's NOT CAUSED BY EATING SUGAR! Type 2 is what your grandma probably has. BOTH can be managed with modern medicine and you can live a long, healthy life with them.