The Atlantic today on why it was easier to be skinny in the 1980s:

They found a very surprising correlation: A given person, in 2006, eating the same amount of calories, taking in the same quantities of macronutrients like protein and fat, and exercising the same amount as a person of the same age did in 1988 would have a BMI that was about 2.3 points higher. In other words, people today are about 10 percent heavier than people were in the 1980s, even if they follow the exact same diet and exercise plans.

The piece goes on to explore three possible reasons for this: chemical exposure and its effect on hormonal processes, use of prescription drugs tied to weight gain, and excessive meat consumption that alters “gut bacteria” in ways that add up slowly over time.