It's an intriguing question! People of the early 20th century ate too much fat, too much sugar, too many carbs, too many calories, and yet did not grow obese. T

It's an intriguing question! People of the early 20th century ate too much fat, too much sugar, too many carbs, too many calories, and yet did not grow obese. There is an interesting paper [1] making a strong case that the cause of the 21st century obesity epidemic is an unidentified environmental contaminant which (1) causes obesity in both humans and other mammals; (2) accumulates in major river valleys; (3) started noticeably affecting the US around 1980, and by now has spread worldwide. Some possible candidates proposed for such a contaminant include animal antibiotics, PFAS, and lithium (e.g. in industrial lubricants). [1] https://www.lesswrong.com/posts/6miu9BsKdoAi72nkL/a-contamination-theory-of-the-obesity-epidemic https://www.lesswrong.com/posts/6miu9BsKdoAi72nkL/a-contamin...