Why do you think that people become delusional or have become increasingly delusional in the last 40 to 50 years?
I'm pretty convinced that things like adenovirus 36 infection, phthalate exposure (especially in utero and as a young child) are obesogenic. I do think you're right that people are probably eating larger portions than in the 80's and often eating more calories, but I wouldn't be surprised is a large part of the reason why was because of obesogenic compounds and diseases.
Another reason I find this easy to believe is research on body weight homeostasis is pretty convincing. The leptin system is pretty strong at getting (some) people to eat less after eating more than usual one day and getting them to eat more after eating less than usual. There is also convincing research on what researchers call the gravitostat which, independent of leptin, alters hunger through weight-dependent signals from osteocytes in the large bones of the body.