Check out the food energy comparisons in which Pepsi boasts it contains more calories than a lamb chop and urges consumers to choose the drink over a measly egg or tomato:
Pepsi vs. lamb chop.
Vintage Pepsi Ad
That's because at the time, Pepsi wasn't just Pepsi. It was "The Drink With Quick Food Energy."
Quick Food Energy!
Vintage Pepsi Ad
During the energy-depleting days of World War II, the idea was that Pepsi's many, many calories would make the difference in manufacturing, ensuring that "American energy will win!"
For the win: calories!
Vintage Pepsi Ad
As the ad claims, soda was the way to get through a difficult wartime effort:
A big job requires lots of soda.
Vintage Pepsi Ad
So was this an anomaly? No. It was, at the very least, part of a Pepsi campaign that lasted through 1944 and part of a culture in which calories were often marketed as a positive (like ads for Hershey chocolate bars that bragged they were "more sustaining than meat"). True Diet Pepsi didn't show up until 1964.
That said, it didn't take long for the tide to change. Less than 10 years later, the February 15, 1953, issue of the New York Times has an ad that boasts a soda was "reduced in calories":
A vintage ad promotes a new and lighter sensibility.