[beagle3]

> Cut calories enough, you will lose weight. Raise them enough, you will gain.

That's true in the useless tautological sense.

I've read a case study a few years ago about someone who has to eat something like 10,000 calories a day, because after some serious illness, their body only takes in 20% or so.

Paper is also carbohydrates - albeit not ones that our gut can process. Any statement about "caloric intake" is so hard to measure to make statements about "caloric balance" vague. They are useful as a "small signal"[1] approximation around common steady states (which are often 1000-3000/kcal a day, although that's not a good characterization).

However, when you go away to this state, this approximation breaks down and stops working. A model that would have predictive power in the "large signal" setting would have to take your entire biomass (10 times as many bacterial cells, although only 10% of body weight; 30% or so of solid excretions; facilitators of many processes), and nonlinear effects of insulin, ketosis, and others.

[1] http://en.wikipedia.org/wiki/Small-signal_model