Are weights on package labels correct?

Nutrition Research Newsletter, Oct, 2004

In situations such as disease therapy and research, the careful control of food is mandatory. When planning such diets it is convenient to rely on the information provided by the manufacturer on the food label. However, there is no research investigating the consistency of food weights as packaged over the time course of an experiment. Product weight of packaged foods, as stated on the food label, is scrutinized by several government jurisdictions and is limited to detection of shortages in weights.

A comparison study of the actual and label weights of portion-controlled food items and foods consumed as discrete units of larger packages was conducted. The goal was to evaluate the reliability of label weights as surrogates for actual weights in foods commonly used in controlled diets in a research setting. Foods studied were selected arbitrarily. All food was provided to the subjects and was purchased form a foodservice company or a local grocery store. Two categories of packaged foods were studied. First, prepackaged portion-controlled foods included both single-serve containers and individually packaged products within multiserving containers. The second group can be described as discrete units enclosed within larger packaging, such as sliced bread or luncheon mean and single pieces of bakery or breakfast products. All foods were weighed by dietary professionals. Packaged food items were taken from different cases and a variety of lot numbers.

There was no statistical difference between actual and label weights for only 37 food items. The actual weights of 15 portion-controlled food items were 1% or more less than label weights, making them potentially out of compliance with federal guidelines.

Well-controlled studies should be able to include portion-controlled food items and discrete units. Nutritionists should instruct individuals with diseases needing a controlled diet to cheek package weights against actual weights to verify information.

J. Conway, D. Rhodes, W. Rumpler. Commercial portion-controlled foods in research studies: How accurate are label weights? J Am Diet Assoc; 104:1420-1424 (September, 2004). [Correspondence: Joan M. Conway, PhD, RD, USDA: ARS: BHNRC, Diet and Human Performance Lab, Bldg 307B, Room 213, Beltsville, MD 20705. E-mail: Conway@bhnrc.arsusda.gov].