Nonnutritious means lacking in nutrients or not providing any nutritional value. Its antonyms would include words like nutrient-rich, nourishing, wholesome, and healthful. These words indicate that the food contains a significant amount of essential vitamins, minerals, and macronutrients that are necessary for maintaining good health. Some other antonyms for nonnutritious could also include terms such as beneficial, salubrious, nutritious, and nourishing. While nonnutritious foods may be high in calories, fat, or sugar, nutrient-rich foods provide the necessary sustenance required for a healthy lifestyle. Thus, it is important to choose foods that are antonyms of nonnutritious for optimal well-being.