This is an old article but still a good one. Every day more is becoming known about the effect on the microbiome on weight and health. This research published in 2015 shows that a person would be 10% heavier in 2006 than in 1980 even eating and exercising the identical amount.

These authors question the effects of chemicals, prescription drugs, and a meat heavier diet.

What this article brings up for me (in addition to having fun with the “old economy Steve” meme) is that we’ve known for many years that there were factors besides food intake and exercise affecting weight. Diets didn’t work then and they don’t work now.

Why It Was Easier to Be Skinny in the 1980’s | The Atlantic