Why is there big difference between what is calculated in an experiment & the caloric value on food containers

Question

I am doing a paper of food calories and I am just using Yahoo Answers as another source for my paper. I just needed input to see if they match up with the other information i found.

Answer 1

Food "calories" are in units of kilo-calories.  "Calories" to a chemist are 1/1000 of a food calorie.  

There are around 4.19 joules per calorie ("little c" calorie) and 4.19 kilo-joules per Calorie (food calorie).

It's a stupid notation, in my opinion.

edit:  oh.  that.  Sorry.  You don't say whether which is greater or less.  Depending on the sophistication of your experiment I can see how it could be either.  Assuming you are "burning" the food in a flame or something and capturing all that heat, If the calorie content you measure is more than what is on the box it's because your body doesn't "burn" the sugar all the way to CO2 and H2O so the energy released is less when your body converts the food to energy.  If the calories you measure are a lot less it's because a lot of the heat released when you burn the food doesn't get put into something you can measure (e.g., if you are measuring the rise in temperature of a mass of water, you can get a lot of heat loss because the water doesn't absorb all the heat).  

If I had to guess, I would say the latter is what you measured.