Eventually, you start to ritually check the nutritional labels of newly bought items to ensure serving sizes, etc. meet your requirements, at which point you cease to see a 'food product' and begin to see a combination of 'proteins, fats and carbohydrates'. The question that I always ask myself (especially when I see two identical products with sparsely different nutritional values) is - "how accurate are food labels?"
The Study:
In 2010, researchers at Tufts University conducted an analysis on 40 different foods bought in various restaurants and supermarkets to determine the accuracy of stated energy contents. Their target - 'reduced-energy foods' or those containing less than 500 calories.
You Mean To Tell Me This Label Is Inaccurate?
Their analysis indicated that the number of calories measures nearly always exceeded the number of calories declared on the nutritional labels by the manufacturers and retailers. On average, they contained 8% more calories than the labels indicated. However, the researchers noted that some individual items contained up to 200% of stated values. That's a whopping DOUBLE what was declared on the food label.
The Take-Away:
While it goes without saying that it is impossible to generalize this study to the entire restaurant and food industry, it should make us all think about our purchases of pre-packaged foods. Urabn et al. (2010) note that, if widespread, the phenomenon observed in their research could hamper efforts to self-monitor energy intake to control weight.
The Solution:
While this may be difficult for some, to others the solution will be second-nature. Prepare and cook as much of your own food as possible, using un-refined ingredients and avoid pre-made products. Although the variation of energy-content and macro nutrient composition may vary between each individual vegetable, fruit, etc. depending on factors such as soil composition, etc; you will nevertheless be able to paint a much more accurate portrait of your overall energy intake.
If you have started down the path of calorie counting, the only logical method is to reduce as much error and variance as possible, in order to maximise the effects of your hard work and efforts.
Reference:
Urban, L. E., et al. (2010). The accuracy of stated energy contents of reduced-energy, commercially prepared foods. J Am Diet Assoc, 110(1), 116-123.