Most people, when trying to lose weight, obsessively count the calories from foods they eat throughout the day. Although calorie information is easy to find and many people depend on it, it turns out that calorie information posted in restaurants and even on the back of food packages are not even accurate.
Even if you memorized the exact breakdown of macronutrients of the Chipotle burrito you just wolfed down, nutrition information found in restaurants and even on frozen and packaged foods can deviate (plus or minus) up to 25 per cent from the label claim. Chalk this up to variable serving sizes, the food quality, the food source, the individual constituents of packaged foods (a trail mix, for example), and good ol' human error, to name a few.
Plus, a certain margin of error is to be expected because of how the energy in carbohydrates, fats, and protein is measured, via something called bomb calorimetry. This badass-sounding method analyses the heat energy given off by food when it's quite literally blown up within a sealed container. It's interesting to note that the results for each of the macronutrients come in a tad higher than what we are normally told:
- Carbohydrates: 4.2 cals as opposed to 4 cals
- Fat: 9.4 cals as opposed to 9 cals
- Protein: 5.7 cals as opposed to 4 cals
The discrepancy here comes primarily from the difference in energy that is actually usable by the human body, since individual absorption and digestion rates can vary (and what your body doesn't absorb will be pushed through the -- ahem -- opposite orifice).
Still, this could be inconvenient for those keeping a close eye on their tracking, but Bodybuilding.com (which, full disclosure, I'm an editor at) insists that this is not a major concern so long as you are consistent. If you're still concerned, you can reduce layers of inaccuracy and variables by eating the same foods day in and day out.
Remember that inaccuracies in tracking (either from individual error or mislabeled nutrition information) are inevitable.
How Accurate Are Calorie Counts? [Bodybuilding.com]