Leaky abstractions and false assumptions.
People go back and forth a lot about the usefulness of “Calories In – Calories Out” as a weight loss vs. a weight gain model. People referred to it as a leaky abstraction, or a simplified model that leaked crucial information in the complexities that it discarded. For a while, this confused me.
On one hand, we know the biochemistry of nutrition as well as we know any trivially-verifiable experimental result. For all animals, if they consume fewer calories than they expend, they’ll lose weight as their body depletes their reserves, and if they consume more, they’ll gain weight as their reserves get filled with the surplus.
Calories in, calories out. A simple model. But also an abstraction. When we say “Calories in”, we are pretending that we know that number.
Do we? We get a label on our food telling us the precise nutritional information. How good is that information, really? Do we really eat the recommended portion sizes? And when they tested the food in a calorimeter, how homogeneous was their sample? And the big question; how closely does your individual digestive system’s ability to liberate calories from a specific foodstuff map to the energy released by just setting the food on fire? And how efficient are each of your individual metabolic pathways, for using the calories immediately versus storing them as fat and so on?
And calories out? How many people go and get their resting metabolic rate measured, and then carefully track their mean activity levels? Do you really trust those numbers around how many calories given exercises burn? Most of them aren’t even adjusted for body weight, and the ones that are don’t take into account that different people do different exercises differently, and that there can be really steep cliffs in metabolic results between briskly walking at 3.5 miles an hour versus 4, depending on what you’ve trained yourself to do.
I don’t think that “Calories in, calories out.” is a leaky abstraction. The leak, I think, comes from the fact that the world pretends that it’s easy to know calories in and calories out.