WASHINGTON — Americans are consuming 41.9 fewer calories per day, a total of 17.3 lbs per year, than previous estimates, according to findings in a study of loss of the edible share of food at the consumer level. The study was conducted by RTI International in partnership with the Economic Research Service of the U.S. Department of Agriculture.

The data are used to estimate overall food consumption through the E.R.S. Loss-Adjusted Food Availability estimates of the E.R.S. Because overall availability of food overstates actual consumption, the E.R.S. adjusts that data for losses — nonedible food parts as well as losses that occur from farm to retail, at retail and at the consumer level.

Based on the conclusion that the loss data are “incomplete and need updating,” the E.R.S. engaged RTI International, which has proposed new estimates for loss of the edible share of feed at the consumer level.

“These proposed estimates cover food loss both at home and away from home for most of the commodities included in the series,” the E.R.S. said. “These losses include losses during cooking and preparation (e.g., frying fats); discards due to preparation of too much food; expired use-by/open dates; spoilage; and plate waste.”

The E.R.S. used the data to study how the RTI estimates would affect the government’s per capita estimates of daily calories and pounds available for consumption for each commodity. Higher loss estimates in the RTI data meant lower per capital consumption.

Publishing its findings, the E.R.S. is seeking public comment and proposes to adopt the new estimates for its entire data span (1970 to the most recent year in the series).

While the data offer revisions for hundreds of foods, the impact on grain-based foods was limited. Rather than affirming the accuracy of the previous data, the E.R.S. said RTI was not able to revise estimates of waste when a food product (such as flour) was used principally as an ingredient.

The overall change for each food group would be relatively small, the E.R.S. said.

“The most affected group would be meat, poultry, fish, eggs and nuts, with an annual increase in food available for consumption of 22.3 lbs per person, or 15%,” the E.R.S. said. “The food group with the smallest change would be grain products, with an annual decrease in availability of 2.1 lbs per person, or 1.5%, though RTI could calculate estimates for only three grain products due to data limitations, such as when the grain was used almost exclusively as an ingredient (e.g., various types of flours). Overall, use of RTI’s proposed estimates in the data series would result in a reduction in estimated per capita availability of 17.3 lbs of food per year, or 41.9 fewer calories per day, for the average American.”

The study found widely varying consumer–level food loss among individual foods, driven by a range of factors, including perishability or shelf life, whether the product is used as an ingredient or ready-to-eat and whether the product is to be eaten by children or adults.

Foods with the largest increases (greater than 35 percentage points) in estimated consumer-level loss include fresh pumpkin, dry buttermilk, dry whole and nonfat milk, Swiss cheese, edible beef tallow and lard.
The largest decreases (greater than 15 percentage points) were estimated for chicken, lamb, nonfat cottage cheese, frozen potatoes and veal.

“Changes in consumer-level food loss estimates could stem from changes in food preparation habits and the increase in food consumed away from home or simply from RTI’s use of a different methodology for calculating losses than that used currently by E.R.S.,” the E.R.S. said.

Consumer loss estimates for most grains, including wheat flour, were left unchanged at 20%.

Within added sugars and sweeteners, refined sugar has the largest change in this food group when RTI’s proposed loss estimates are adopted — a decrease in per capita availability of almost 7.8 lbs per year, or 36.8 calories per day, an 18% decrease per person. The data estimated per capita availability of high-fructose corn syrup (loss-adjusted) up by 2.6 lbs per year, or 12.3 calories per day.

Explaining the methodology behind the work, the E.R.S. said RTI first compared estimates of total U.S. retail household purchases with total U.S. at-home consumption for each food in E.R.S.’s Loss-Adjusted Food Availability series.

Data sources included the Nielsen Company’s Homescan data for 2004 (food purchases from retail outlets) and the National Health and Nutrition Examination Survey (NHANES) for 2003-04 (food consumption).

“RTI also calculated alternative estimates of food loss by comparing the total quantity available at the consumer level in the Loss-Adjusted Food Availability series with total reported consumption in NHANES,” the E.R.S. said. “RTI relied on several supplemental data sources to adjust the purchase data to facilitate comparisons with the consumption data. In addition, RTI took direct measurements of count data (e.g., produce sold by count rather than weight), inedible percentages of food, and moisture gains for foods if data were not available from one of the data sources.”

RTI also convened an “expert panel” to provide data for the analysis, including estimates of food loss to validate the RTI estimates (or provide an estimate for foods for which estimates could not be calculated) and estimates of the percentage of each food typically used as an ingredient. Based on the resulting data, RTI provided one recommended or proposed estimate for each food for which an updated estimate could be calculated for use in ERS’ Loss-Adjusted Food Availability data, the E.R.S. said.

In a second phase of the study, the E.R.S. applied the consumer-level loss estimates proposed by RTI for each commodity to the existing Loss-Adjusted Food Availability data.

“Results revealed changes in E.R.S. estimates of the pounds of food avail¬able for consumption per capita per year, and changes in the number of calories available for consumption per capita per day,” the E.R.S. said.

Based in Research Triangle Park, N.C., RTI is a research organization with a staff of 2,800, offering services to governments and businesses in more than 40 countries in the areas of health and pharmaceuticals, education and training, surveys and statistics, advanced technology, international development, economic and social policy, energy and the environment, and laboratory and chemistry services. According to the company, statistics research has been a primary specialty for longer than 50 years.

“Our statisticians, epidemiologists, and bio-statisticians conduct complex statistical analyses to support wide ranging research programs in both laboratory and social sciences,” RTI International said.