Final answer:
Watermelon has the highest glycemic index among the options provided, due to its high sugar content which can lead to rapid increases in blood glucose levels.
Step-by-step explanation:
The nurse should identify watermelon as the food having the highest glycemic index (GI) when developing an educational program about the GI of foods for individuals with diabetes mellitus. Watermelon is high in sugars, which can cause a rapid increase in blood glucose levels, leading to a high GI rating. On the other hand, foods like lentils, whole-grain bread, and brown rice have more complex carbohydrates and provide fiber, which can moderate blood glucose levels.
Brown rice and whole-grain bread contain complex carbohydrates and are recommended for a balanced diet, as they include fiber that slows down glucose absorption, but they have a lower GI compared to watermelon. Lentils are also a better option for people with diabetes due to their low glycemic index, high protein content, and the presence of soluble fiber that can help control blood glucose levels.
In summary, while all these foods contain carbohydrates, which people with diabetes must manage carefully, watermelon stands out as having the highest glycemic index among the options listed and should be consumed with caution.