Tuesday, January 5, 2016

Hunger as an underappreciated factor in nutrition

I've been hearing pretty good things about the newest book in the sometimes-terrible literature on low-carbohydrate nutrition science. It's titled Always Hungry, and is written by physician and Harvard professor David Ludwig.

Without having read the book yet, I am pleased to see that 'hunger' is gaining recognition as a powerful factor that influences nutrition, weight regulation and metabolism. Many scientists and public figures who advocate low-carb diets--notably Gary Taubes--make the case that the 'calories in, calories out' model of weight regulation is wrong because it contains no pertinent causal information.

Part and parcel of this critique is the idea that the common-sense causal pathways might in fact be reversed: instead of overeating and sloth causing fatness, fatness might cause overeating and sloth via metabolic disregulation.

A scientific model is essentially a simplified version of reality: it helps us uncover causal mechanisms by sorting important details from unimportant ones. I see the failure of the 'calories in, calories out' model of weight regulation as basically undervaluing the causal power of two channels: appetite and energy availability.

On appetite, it seems pretty clear that the vast majority of people cannot voluntarily endure hunger for long periods of time. Recognizing that different types of foods affect the regulation of appetite (i.e. carbohydrates make you hungry) is huge missing piece in many approaches to weight loss.

Similarly, the general concept of energy availability and how it differs among individuals is underrated. Different foods affect the body's energy partitioning process differently, and a poor diet will divert too many calories towards storage. This leaves insufficient energy available to do awesome stuff like go exercise or muster the willpower to resist unhealthy food. As a side-note, I suspect many highly-productive people have tangible biological differences in their ability to convert consumed calories into movement and thought. If you're brimming with energy, it's doubtful you'll zone out for five hours on a couch watching netflix.

So the 'calories in, calories out' theory is trivially correct, but the emerging consensus about its causal vacuousness is the deeper insight. A diet's effect on the causal pathways of appetite and energy availability are very likely more consequential towards a person's overall body weight than their mental commitment during moments of reflection to 'lose weight'.

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