that's the macro change, yeah, but the rate of increase in obesity in the us got sharper after the 80s, so it doesn't feel like the complete picture to me.
we got the abundant food and the largely car bound live cycles and it still kept getting worse for decades after that point. I suppose it could be generations growing up only knowing this and so habituated to it more?
The ability to experience endorphins from things unrelated to food has gotten more expensive. Would you rather buy a $13 dollar move ticket and go hungry, or just buy a $13 McDonald's meal and go home to watch a movie? Buy a $75 dollar ticket to a special event? Buy several thousands of dollars in travel? Food is much easier to fill the gaps in feeling good.
The "public presence" of society has diminished due to the internet. You no longer need to put effort into constantly looking your best because social media helps curate your appearance. Going to Walmart is now so relaxed that you can wear pajamas. Putting on your "best appearance" occurs elsewhere in curated ways (i.e. facebook/instagram posts and careful selfies). You can "partition" your social life so that the people shopping at walmart see pajama-you while the Tinder matches see someone totally different.