Final answer:
The main contributor to the increase in daily caloric intake in both men and women between 1971 and 2000 was the increase in carbohydrate intake.
Step-by-step explanation:
The main contributor to the increase in daily caloric intake in both men and women between 1971 and 2000 was the increase in carbohydrate intake. According to the information provided, most of the extra food energy came from an increase in carbohydrate consumption, particularly from sugar-sweetened beverages. These beverages, which include soft drinks, fruit drinks, sweetened iced tea and coffee, and energy and vitamin water drinks, accounted for almost 25 percent of daily food energy in young adults in the United States.