a cal is the amount of energy required to increase the temperature of 1 gram of water in 1 C grad.
Well, a Kcal is the amount of energy required to increase the temperature of 1000 grams of water 1 C grad.
Actually, ALL the cal readings for food refer to Kcals, not cals (cals are normally used in laboratories). However, it works in both ways, what you burn with exercise are also Kcals, so not need to freak about it.
I think that for ease of understanding and not to confuse the average consumer ("Hey, this thing has 20.000 cals/gram, I better not eat it") manufacturers decided to conveniently drop the K.
Look closely at food tags, some of them are in Kcals.
I never knew that! Wow, I guess you learn somthing new everyday. I have another question about the calorie system: Food is labeled with a certain amount of calories, does that amount refer to the energy released in digestion? Or do they do it by combustion in a bomb calorimeter, or total chemical energy of the food? Just something that has left me curious for a while. Thanks!
I understand it is is the energy stored in the food. I haven't read how they do it, but I always thought, they kind of "burn" the food and measure the amount of heat created, or some other method.