The rainbow watermelon smoothie is a healthy, refreshing, and filling drink that’s great for weight loss. This smoothie is packed with vitamins and minerals and will help you feel full and satisfied until your next meal.This smoothie is great for those who are trying to lose weight because it contains no added sugar, yet still tastes sweet. You can make this recipe using fresh or frozen watermelon, but if you are using frozen, make sure it’s thawed before blending.