FAQs about the most energy-dense source of calories in the human diet What is the most energy-dense source of calories in the human diet? The most energy-dense source of calories in the human diet is fat. Fat contains 9 calories per gram, making it the most concentrated source of dietary energy. More information about energy-dense foods Are all fats considered energy-dense? No, not all fats are considered energy-dense. While fats, in general, are the most concentrated source of calories, certain fats like saturated fats and trans fats can be less healthy and should be consumed in moderation. Learn more about…