Dr. Chris Knobbe links the surge in chronic diseases—like obesity and diabetes—to the rise of seed oil consumption. From 1922–1987, obesity rose 600% while seed oil intake jumped from 78 to 497 calories/day. Seed oils damage metabolism, promote inflammation, and are nutrient-poor. Once used as machine oil, they now make up ⅓ of U.S. calories. To avoid them: skip packaged foods, eat whole foods, and cook with healthy fats like butter or olive oil.

In the last few decades alone, vegetable oils have overtaken many times and almost supplanted other fats from our kitchen. According to...