Is absurd that we essentially have a regressive income tax. I also wouldn't ignore the global environment during that period.
During those decades, the US was effectively the only industrialized nation in the world. Everyone else either never had factories to begin with, or had smoldering piles of rubble where their factories used to be.
Physics tells us that CICO predicts weight gain and heaps of empirical data tells us it's one of many relevant factors.
Most people don't really control their weight by counting calories. They go by how they feel and our feelings,are heavily influenced by our biochemistry. Semaglutide doesn't work by giving people will power or self control; it works by targeting GLP-1 receptors to make them feel full sooner.