Why don’t my macros add up to my total calories?
Generally speaking, protein, carbohydrate, and fat contain roughly 4, 4, and 9 kilocalories per gram, respectively. However, if you calculate your total daily Calories by multiplying your macro totals and summing them, you’ll likely find some degree of disagreement – the Calories calculated based on macronutrient intakes don’t perfectly match the Calories provided from food labels and database entries.
So, what gives?
This discrepancy is intentional, and is not an error or a bug within the app.
There are several ways you could seek to quantify the Calorie content of a food, such as labeled Calories, Calories from bomb calorimetry, Calories calculated from macronutrient weights using specific heats of combustion (fat: 9.4 kcal/g, carbohydrate 4.1, protein 5.65), or Calories calculated from macronutrient weights using general Atwater factors (fat: 9 kcal/g, carbohydrate 4, protein, 4). You could even get into more granular detail by using food-specific estimates, which account for the fact that the general Atwater factors are rough approximations, and the true metabolizable energy yield from carbs, fats, and proteins vary from food source to food source.
The point is, there are many different ways to calculate the Caloric content of the food, and they won’t all necessarily match up perfectly with your macro-based calculation using general Atwater factors (4, 4, and 9 kcals/gram). In reality, they actually shouldn’t match up when we’re trying to make calculations related to energy balance.
The biggest factors contributing to discrepancies between labeled Calories and Calories calculated based on macronutrient totals involve alcohol, fiber, and sugar alcohols. If you consume an alcoholic beverage, the Calories from ethanol (7 kcals/gram) count toward your daily total, but don’t fit into carb, fat, or protein totals. Similarly, nutrition labels tend to count fiber and sugar alcohols toward the “carbohydrate” total, but they yield fewer than 4 metaboilzable kilocalories per gram.
Nutrition labels and database entries aim to provide a Calorie estimate that represents the metabolizable energy content of the food or beverage. In doing so, they often attempt to correctly quantify the Calories that will actually be absorbed from things like fiber and sugar alcohols, rather than pretending that the human body will absorb 4 kilocalories per gram from all of them. After all, when it comes to energy balance, only the calories that actually get absorbed are impacting total body energy.
It’s worth noting that Calorie labels are given a fairly generous margin for error in terms of their reporting, and this is often pointed out by people suggesting that you should be calculating Calorie intake based on macros instead of labeled Calories. However, the macronutrient values of foods are also subject to estimation errors and rounding errors, and the general Atwater values themselves are rough approximations, so this reasoning doesn’t really hold up.
While it may feel more "congruent" to look down and see a perfect combination of macro totals adding up to the listed Calorie total, and this may satisfy some perfectionist tendencies, this congruency doesn't actually reflect greater accuracy. In fact, it’s pretty easy to see how this approach to Calorie calculation inflates your total Calorie number in the context of, for example, a high-fiber diet.
Don’t get us wrong; it totally makes sense to set some rough macro guidelines based on your total Calorie allotment, which is why we do it in MacroFactor. Nutrition coaches and apps have become fond of providing macro targets because it’s a simple and concise way to convey nutritional objectives, and total daily intake of metabolizable energy will be fairly consistent as long as you’re getting close to your macro targets and your intakes of things like ethanol, sugar alcohols, and fiber are consistent.
So, Should You Aim for Your Macro Targets or Your Calorie Target?
The MacroFactor team generally prefers to aim for our daily Calorie and protein targets, while roughly achieving our desired ratio of carbs to fats. This approach is easy, practical, and most closely aligned with the core functionality of MacroFactor. However, if you prefer to aim for specific macro targets rather than Calories, that’s totally fine as well. If you go that route, you’ll just want to be very consistent with your daily sugar alcohol and fiber intake, and you might want to manually log alcohol as a Calorie-matched serving of pure carbohydrate (for example, instead of logging a 100-kilocalorie alcoholic beverage, you’d log 25 grams of pure carbohydrate, which would yield about 100 kilocalories).
We could give users the option to use macro-calculated Calories instead of labeled Calories, and we might someday, but that merely serves to reinforce the illusion of greater accuracy rather than actually improving accuracy. Plus, striving for impractical levels of tracking perfection is kind of antithetical to our mission with MacroFactor. When possible, we wish to dissuade users from stressing over granular details and trading quality of life and peace of mind in exchange for a trivial increase in accuracy. We want an app that supports and assists users on a rewarding journey that leads them toward achieving goals, rather than an app that pressures and restricts users on a stressful journey that leads them toward agonizing over immaterial details.
So, whether you prefer focusing on your Calorie target or your specific macro targets, we encourage users to pick a strategy that helps them achieve their goals with the least amount of stress. Also, whichever route you choose, you’ll want to make sure you’re getting fairly close to your protein target on a consistent basis, and consistently staying above your lower limit for fat intake. Most importantly, try to remember that no matter which method you use for quantifying Calories, some degree of inaccuracy is unavoidable. Stressing over perfection is discouraged, because there is truly no route that is free of estimation or rounding errors.