> Just because directly calculating your exact calorie balance is untenable It's not only untenable, it's infeasible. The only way to "directly" calculate one

> Just because directly calculating your exact calorie balance is untenable It's not only untenable, it's infeasible. The only way to "directly" calculate one's energy expenditure is to either place them inside a direct calorimeter or to use respiratory gas analysis, and to adhere to very strict protocols. And no, fitness bands and watches are not accurate enough to overcome the margin of error. Sure, one can keep lowering the amount of food they eat until they get some kind of result from it. In that case, there's almost no point in trying any sort of BMR calculation flim-flam whatsoever. They'd be better off just eyeballing how much they eat and reducing the volume and the frequency. Regardless, my point stands. Suggesting that the answer is to "simply" intake ~150 fewer calories of energy per day is to suggest that the vast majority of people are equipped with the skills and knowledge to even get close to that kind of accuracy in any sort of calculation. Maybe one can get lucky and see results from such a "simple" calculation because of their individual biology and eating habits, but the margin of error is still very high. Let's set aside reality for a moment and pretend that calorie counts on packaging were perfectly accurate and that the Harris-Benedict equation works perfectly for everyone. That still wouldn't matter the inference of calories of food are/were measured as heat in a bomb calorimeter (i.e. setting food on fire and recording how much heat is emitted). The calorie count that appears on a food package is a guess based on the composition of macronutrients. With the exception of fiber, the calories of fat, protein, and carbs are combined together to form the single count based on how they typically burn in a calorimeter. This introduces more inaccuracy depending on the type of fiber since it may be fermented into digestible substrate. The human body is nothing like a bomb calorimeter. It treats different forms of energy differently, and different forms of energy are utilized to varying amounts, and are even utilized differently in the presence of one another. If you take a dump, let it dry and then light it on fire, it will burn because there's excess energy being passed through and not converted to heat by the body. Food may pass faster or slower depending on what it's composed of. Fiber can not only do that but also prevent the digestion of nutrients. A diet that mixes lots of fat and carbs together facilitates the storage of more energy as fat than if either of them were eaten in isolation. Protein has more of a thermic effect (the body emitting more heat) than either carbs or fat. Point being, if one really does not want to lose weight by actually choosing to eat foods that are appropriate for their digestive system, or to eat food that is low in energy density (ex. leafy greens), then they might as well cut down on food to such an extent that they would be able to notice it without punching numbers into a calculator. A substantial amount would have to be reduced from the diet to have a reasonable amount of confidence that one is indeed eating less energy than the body is expending in a day.