Is there a device that will use calories to operate machines?

Just an Idea though, cause I'm fat but I'm going to gym for half a year now but I just wondering if there's a device that would use my calories or fats to operate machines? For example turning my fats to energy for computers? Or to use my calories to charge my iphone?

There are flashlights that charge from being shaken, and radios that charge from a crank being turned. That's your calories being converted to electrical voltage. Bicycles are machines operated by human calories, your food calories are converted to the kinetic energy of you and the bicycle.

There have been machines made to burn food as fuel. If I remember right, they're inefficient.

More generally, calories are just a unit of energy (like joules), so technically any device that does anything uses calories.