Eating fat makes you fat. No, eating carbs makes you fat. Actually, it’s a simple equation relating calories in and calories out. Such endless debates about presumed dietary culprits or cures for obesity have led to widespread public confusion and mistrust in nutrition science. But what is the truth? In this presentation, Kevin Hall, PhD, will discuss the physiology of body weight regulation and how we adapt to various changes in diet. The total calories we consume, eating carbs versus fat and differences in diet quality—which varies with the amounts of “ultra-processed” foods we consumer—will be discussed.