Food packets usually say 'kilocalories', but running machines and TV adverts always 'calories' - what's going on?

This question has been annoying me for ages. Enough that I had to look it up.

A "food calorie" (or "large calorie", or "Calorie") is equal to a thousand "small calories", hence kilocalorie (kcal). Wikipedia helps to clarify the issue:

"Some advocate the convention of the capitalizing the C in these so that one Calorie is equal to 1000 lowercase calories, but that convention is not generally followed. The large Calorie is sometimes abbreviated kcal, to indicate clearly that is 1000 times as large as the small calorie formerly common in chemistry and physics usage. Consequently, the prefix kilo- is not used with large Calories. Food calories are also more specifically called kilocalories on the basis of the small calorie usage. This term, which makes it clear that large calories are intended, is widely used by professional nutritionists when speaking in terms of calories rather than joules, but the term kilocalorie for the large calorie is less often used by laypersons."

I wish I was making this up.

In Australia they use kilojoules instead, I learn. How sensible.

This post was originally on LiveJournal.