This article takes up a common position that calories are "wrong" because, due to our bodies' complex natures, such an arbitrary measure ignores a lot of what is going on. And yet, every time this view is expounded, someone comes up to calories' defense, saying that they are a reliable measure of nutritional energy. So which one is right?

While it is true that calories don't measure the nutritional energy absorbed in any single meal, that would be a trivial proposition. Calories are a statistic, that is, an estimate of an unknown but posited number, and partial representation of an underlying distribution. Saying that calories are "wrong" in this sense would be merely stating that they are possibly wrong. And they would be wrong, if the underlying processes are somehow consistently correlated with each other, which would produce inconsistent and biased estimates of caloric content.

Yet, I don't have any reason to believe that the probability that I buy some potato cultivar today is correlated with the composition of my gut flora three weeks in the future, much less that it would be consistently so. On the contrary, the factors supposedly affecting my nutrition according to biologists are so many, and so diverse, that I might as well appeal to the central limit theorem, in which case calories would be just as a good measure as we can have. If today some potato gives me 166 kcal, and tomorrow 158, and further on 163... I don't see what's the issue. The likelihood of a critical event, such as starvation, due to misreporting of calories or due to some feature of my constitution seems so low that I would only very likely trigger it if I ate nothing but one type of food, in the same quantities, for a long period of time.

Furthermore I will never understand those who prefer no measures to at least one rough measure. No things are created perfect, but only made better. I wonder would have happened it occurred to Eratosthenes that his measure would have been too rough, too imprecise, or too vague for his mind. If all ancient mathematicians were bothered that no "real" triangles were to be found anywhere, mathematics wouldn't have happened at all. By such strict understanding of measure and precision, of course measures fail. They couldn't possibly live up to it. An other example is personality theory, which is said to have been nearly abandoned at it's inception because some psychologists thought of it entirely in terms of archetypes, rather than a general description of probable behavior.

And lastly, if calories have been adequately defended here, then I'll also add that ogling at them in order to find what is wrong with nutrition theory seems completely wrong. We already know about calories, and they are a measure of what we know. Rather than looking at them, we should be looking at the measure of our ignorance, which is the error term. If some calories consistently fail to account for some observations, then it's because no one has looked inside the black box enough to figure out what is going on.

In short, it's a sensational headline. The only people who perhaps should be worrying if calories are "wrong" in the sense of not being accurate to the tenth decimal are Soylent-ers.