Improving the overall quality of one's diet helps to prevent type 2 diabetes, independent of other lifestyle changes.

The study also examined whether improved diet was a marker of other lifestyle changes, such as weight loss or increased physical activity, or if it could independently reduce a person's risk for developing type 2 diabetes.
"We found that diet was indeed associated with diabetes independent of weight loss and increased physical activity," said lead researcher Sylvia Ley, PhD, a post-doctoral fellow at the Harvard School of Public Health. "If you improve other lifestyle factors you reduce your risk for type 2 diabetes even more, but improving diet quality alone has significant benefits. This is important because it is often difficult for people to maintain a calorie-restricted diet for a long time. We want them to know if they can improve the overall quality of what they eat – consume less red meat and sugar-sweetened beverages, and more fruits, vegetables and whole grains – they are going to improve their health and reduce their risk for diabetes."
The study also showed that it didn't matter how good or poor a person's diet was when they started out, she said. "Regardless of where participants started, improving diet quality was beneficial for all."
Source-Eurekalert