If a snickers bar has 500 Calories, is that taking into account my bodys (25% ?) inefficiency ? So, hypothetically, if you had a space ship that ran off candy bars and was 100% efficient, are there really 2000 calories in the candy bar ? But they only write 500 on the label because that's all my body will actually use ? Or will my body only use 25% of what's printed on the label ?