There are approximately 3,500 food calories in one pound of human body fat tissue. A food calorie is equivalent to 1,000 thermochemical or heat calories; therefore, there are 3.5 million thermochemical calories in one pound of human body fat.
The heating value of a substance can be used to calculate how many thermochemical calories are in one pound of that substance. The heating value, usually given in units of energy per mass, indicates how much energy is released when a unit mass of that substance is completely combusted. The amount of food calories in one pound of food can generally be calculated from the nutrition information.