Dr. Ron Najafi argues that calories measure heat, not the ATP energy your body actually uses. Different foods with the same calorie count produce different amounts of usable energy, so a calorie is not a calorie biologically.
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That a calorie eaten is a calorie eaten, then it depends on where those foodstuffs came from. And the reason is because we don't run on heat, we run on chemical energy called ATP, adenosine triphosphate. And how much ATP you generate is really the indicator of how many molecules of energy you actually get out of food. That's not heat. So from the standpoint of what it is you're measuring, calories are actually irrelevant. Okay. Turns out different foods will generate different amounts of ATP based on different properties of those foods. And I have, you know, explained this in, you know, podcasts before, so this isn't new.