The way you're using thermodynamics to support your point is wrong, you are asserting that the human body is a closed system, which of course it is not. A human

The way you're using thermodynamics to support your point is wrong, you are asserting that the human body is a closed system, which of course it is not. A human will absorb and excrete carbohydrates,fats and proteins at differing rates depending on a bunch of factors. To simplify the human metabolic process down to a simple (in)-(energy burned)= zero equation is completely false, as again, the body is not a closed system.