In this article, I want to look at a somewhat fundamental aspect of general nutrition; that is the distinction between calorie intake, nutrient intake, and food intake. This is relevant for the simple fact that the average person doesn’t think in terms of calorie intake, and they probably don’t think in terms of nutrient intake. Rather, they think in terms of eating food; thus it’s important to examine the distinction between those three “categories” of intake.
Ignoring the fringe that claims that the calorie counting theory is invalid or doesn’t work, most diet books deal predominantly with calories (everywhere but the US, joules are used). They’ll discuss caloric intake (from food) or caloric expenditure (from activity) or compare the two. In discussing what is happening to the body (weight gain or loss), they’ll compare the energy balance equation which compares calories in to calories out.