Friday, January 21, 2011

The Calorie-Why is it a bad stat?

There are three types of liars: Those that lie intentionally for personal gain, those that lie because they are ignorant, and those that lie intentionally to protect others.

Of the three types I put calories in the category of lying out of ignorance. Basically knowing the information of the quantity of calories within some food tells you little about it's actual worth to you. Which means tables like the one below paint an incomplete picture.

The calorie is a measure by which a substance can raise 1 gram of water 1 degree Celsius. In nutritional contexts, however, the small calorie is too small a unit to be useful; so the term calorie is used for the large calorie, as is the equivalent term kilocalorie (symbol: kcal), being 1000 small calories = 1 large calorie.

This however does not mean that it is the amount of energy or usefulness that your body will extract from some food. A simple heuristic sums up what I'm trying to get at:

"It takes money to make money."

Or in the case of food what you want to know is the energy/resources you have use to get the energy/resources you want to gain. In addition you also want to know how much time it takes you to process a food because as Benjamin Franklin once said:

"Time is money. "

So I want to use these two simple rules of thumb to start the stat which will better describe a food you are trying to eat for energy gain. My initial thought was something like

Food Edge = (calories/(Glycymic load(measures insulin use intensity)+ other processing costs/time)) + beneficials +nutrients(units/ g)+minerals(units/ g)-long term consequences per use

There is a similar example from the world of saber-metrics that would also be familiar to anyone who collected baseball cards in their younger years(as I did). There was a particular stat that was always listed that has been shown to be of dubious use : batting average. Batting average tells you how frequently someone got a hit off of the opposing pitcher. What it did not tell you is how good that hit was, or how frequently a batter gets on base vs the opposing pitcher via a walk(an equally valuable feat as getting a hit). So it is a similarly ignorant statistic. The better statistic, called OPS, was first popularized in 1984 by John Thorn and Pete Palmer's book, The Hidden Game of Baseball. OPS stands for on base percentage + slugging percentage which accounts for walks, the intensity of hits, sacrifice flies and the negative value of strikeouts.

The lesson I learned from this example is that a statistic has to value similar feats equally, it has to account for both the frequency and the intensity of great feats and devalue negative feats(like strikeouts). With my food statistic I will try and do the same.

BTW if anyone reads this and has a suggestion for a better name than Food edge please chime in. My other thought could be to call it Food Energy Ratio.

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