Claire runs cross country in college. She knows she needs adequate carbohydrate to keep her body fueled. Typically, her food intake consists of cheese sticks and a glass of orange juice for breakfast; a peanut butter sandwich, apple , bag of pretzels, and sweetened tea for lunch; spaghetti with marinara sauce, garlic, bread, salad, and a glass of milk for dinner; and an orange for her evening snack. Lately, she is feeling tired and has to wear a sweatshirt in class to keep warm. She is also having trouble concentrating. What do you think is causing Claire's problem and why? What would you recommend?