A calorie is a calorie only if it is incinerated in a bomb calorimeter, and the heat given off measured. Biologically derived calories from different foods have entirely different metabolic effects on the human body. Equal calorie portions of sugar, alcohol, meat or olive oil have widely differing effects on hormonal systems such as insulin, and satiety signals such as cholecystokinin or peptide YY. It is irrelevant how many calories a portion of food on a plate contains.