Watermelon lives up to its name big time. This colorful, refreshing fruit, with its dramatic light-and-dark-green rind and its juicy pinkish-red interior, is actually over 91 percent water, which makes it super low in calories: 1 cup of diced watermelon contains a mere 46 calories.
No Guilt Here
Watermelon has almost no fat or protein. Most of the fruit's 46 calories come from carbs. At 11.63 grams per cup, primarily from natural sugars, carbs give watermelon its sweet taste. A cup of melon isn't going to contribute a lot to your daily calorie count, given that the recommendations for daily calorie consumption start at 1,000 grams for 2-year-olds and go up from there. Adults need anywhere from 1,800 to 3,200 calories a day, depending on age, gender and activity level.