Nutrition food labels do their best to be as accurate as possible, unfortunately, most are not accurate. A study from Jumpertz et al (2013) found that most calorie reporting on food labels were significantly inaccurate.
Food labels do their best to report the metabolizable energy in food (which is the total caloric content you can absorb, not the gross caloric content), not the actual energy (gross calories) in food. What is metabolizable energy? The amount of calories we actually use in our bodies from the food we consume (which is not 100% of calories, actual energy, that makes up a food product).
Same with vitamins and minerals, like Cliff Bar company, who only reports the amounts of vitamins and minerals they add back into the finished food product. They do not include the vitamin or mineral count found naturally in the food for fear of being sued (since food changes seasonally and vitamin and mineral content naturally in food varies month to month).
It’s the same with calories. For example, the Hershey’s bar has 30% of calories we don’t use (can I get a hell yes from my fellow chocolate lovers?!).
The Food and Drug Administration (FDA) allows calorie content to exceed label calories by up to 20%. In the research study mentioned, the investigators found the absolute amount of calories in food is higher than the calories stated on the label (falling within that FDA approved 20% more category). Since nutrient absorption has a high variability in humans from person to person (some people absorb more nutrients differently than others), it may be beneficial to report the total (gross) caloric content of the food on food labels, instead of what was deemed metabolizable energy by the food companies.
Check out the link below for the study and some pretty mind-blowing figures of some common foods we enjoy!
https://onlinelibrary.wiley.com/doi/full/10.1002/oby.2018
