If you are concerned about watermelon being high in sugar, consider this. If you look at the glycemic index (GI) of watermelon, it's listed high with a 76-80 score, meaning high sugar (1-100 scale). If you look at the glycemic load (GL) which is a 1-10 scale, it's only listed as 5. Glycemic load gives you a more accurate picture of a food's (in this case the GL of watermelon) real-life impact on your blood sugar. Watermelon can be a sweet as well as nutritious part of your summer diet.