Back then there wasn't as many fat people as there is now.
We have not always been a nation in the midst of an obesity epidemic. In the 1960s and 1970s only 13 percent of U.S. adults and 5 to 7 percent of U.S. children were obese. Today, 17 percent of our children, 32 percent of adult males, and 36 percent of adult females are obese.