What most people consider to be a single-serving bottle of soda has 2.5 times the calories reported on nutrition label.
NUTRITION Fighting a craving for less nutritional snack food, I found myself comparing bags of pretzels. The store brand had 450 grams of sodium per serving. For half a buck more, a national brand boasted 300 grams. I was nearly persuaded to choose the "healthier" option before asking the question, "How much is a serving?" It turns out that the national brand counts 11 pretzels as a serving, whereas the store brand considers 23 pretzels more realistic. Hence, the store brand actually had 25 percent less sodium.
It's not just pretzels either. Vitaminwater has been berated for listing its nutritional information with servings for a fraction of the bottle contents.  Major food manufacturers, including Kellogg, Kraft Foods and General Mills rolled out their so-called Smart Choices in 2008 for processed foods like Froot Loops, Cocoa Puffs and Kraft Macaroni and Cheese. 
The FDA plans to research whether one particular approach would make it easier for consumers to select healthy foods. Hamburg pointed to the success of the U.K.'s traffic light system, which uses red, yellow and green lights to highlight nutritional quality. 
Until a consistent system is available, consumers must become vigilant in reading nutritional labels — perhaps bringing calculators. When preparing portions at home, a measuring cup may be used to achieve nutritional goals. Discrepancies on food labels may also encourage brand loyalty; after investing considerable time determining which product is the best choice, future trips to the grocery store are shortened by avoiding competition vying for attention.
Nutrition labels differ among various countries and every food does not have one.  It is only required on mechanically processed foods. So labels are absent on fresh produce. At popular fast-food franchises, nutrition facts are often available upon request at the counter or by visiting the company website. A site called The Daily Plate attempts to coach visitors to reach personal goals. 
Take-away tip: Compare serving size.