Is there a device that can measure calories in food?

a calorie counter.... it's a book. really good. has everything in there.

there is a device called a bomb calorimeter. Basically the food is put into this completely sealed chamber and the chamber is ignited (all the food is converted to ash), and the outer layer of the calorimeter is immersed in water, so they measure the temp the water rises from the heat released by the food when it is combusted, and they use this equation to work out the energy released by the food (basically the energy (calories) in the food are converted to heat energy and this is measured). But you need to make sure that none of the heat escapes (which is why the devices have to be sealed very well), otherwise you'll get a lower energy calculation than there actually is. A bomb calorimeter can be used to measure heat energy released from anything (not just food substances) hope this answers your question :). although you're probably wanting to eat the food after the calories have been measured, lol and this device is probably not good for that (unless you really like eating ash).