Final answer:
Americans have significantly increased their daily calorie consumption, particularly from sugar-sweetened beverages, leading to rising obesity rates.
Step-by-step explanation:
From the data provided, it seems that the average daily calorie consumption by Americans has noticeably increased over time. Historically, a worker in the 1600s could afford 2,500 food calories, which sufficed for the daily needs based on height, weight, and gender. By the 1800s, this capability had doubled to 5,000 food calories due to economic growth. However, between 1971 and 2000, Americans have been consuming significantly more calories, with women increasing their intake by 335 calories per day and men by 168 calories per day. This change has contributed to the doubling of obesity rates during that period, from 15 to 31 percent.
Primarily, the additional calories consumed have come from increased carbohydrate intake, especially from sugar-sweetened beverages such as soft drinks, fruit drinks, sweetened iced tea, and other similar beverages, which now account for nearly a quarter of the daily food energy in young adults in the United States.
Calorie Affordability and Economic Growth
Alongside the increase in calorie consumption, there has also been a dramatic rise in the number of food calories that people can afford.