Nick NorwitzMD PhD, Oxford-Harvard | Metabolic Health Educator | “Stay Curious”

Why ‘Calories In, Calories Out’ Is Pseudo-Science

23 Oct 2025 · 1 min

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In this monologue, the speaker argues that calories are merely a unit of measurement—a post‑hoc descriptor of weight change—rather than a causal driver of obesity. He contends that the popular “calories in, calories out” (CICO) framework is not a genuine scientific model but a simplistic accounting tool that frequently fails to predict real‑world weight dynamics. When the CICO premise breaks down, he observes that practitioners resort to convoluted rationalizations, likening them to absurdly precise bomb‑calorimeter experiments to force the numbers to fit. The overall tone is sarcastic and critical, emphasizing the inadequacy of calorie‑centric thinking for understanding obesity.

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Calories cause obesity like an odometer causes driving. Calories are a unit, a measuring stick. They can be an after-the-fact mathematical description of weight change as a best-case scenario, but calories in, calories out, it's not just a wrong model of weight change and obesity. It's not a model at all. And every time the calories pseudo-model breaks, and it does a lot, people conduct these mental gymnastics to justify it, almost as if they're going to fiddle with your feces in a bomb calorimeter to determine the exact number of excreted calories that make the equation work. That said, if any coach or nutritionist or otherwise is willing to go that far for a client, I'll eat my