...From the pages of Agricultural Research magazine
A new computerized interview
process developed by the ARS
Food Surveys Research Group
prompts nutritionist Alanna
Moshfegh to ask survey
respondents about "forgotten"
foods. The mounds help
respondents estimate portion
Some folks go to great lengths to
remember important anniversary dates and tasks. But many find it surprisingly
difficult to remember what foods they ate just yesterday.
The ARS Food Surveys Research Group
(FSRG) has developed a method for achieving nearly total recallat least
for what's been eaten. The 30-member group is part of the Beltsville (Maryland)
Human Nutrition Research Center.
The group's mission is to plan, design, coordinate, and manage the U.S. Department of Agriculture's nationwide food surveys. Before 2002, this included the well-known Continuing Survey of Food Intakes by Individuals, among others. The FSRG has now produced an innovative survey instrument, called the Automated Multiple Pass Method (AMPM), which helps people remember and report the foods they ate over 24 hours. It consists of a specialized software program, operated by highly trained interviewers. The method is now the primary instrument used to collect dietary food intake data from individuals sampled in the United States in national surveys.
This two-dimensional drawing
represents foods that mound
on a plate, such as casseroles,
vegetables, and rice. The plate
and knife provide a size
"This finely tuned
instrument helps ensure that we are using the best possible method to collect
accurate information on what we eat in America," says nutritionist Alanna
Moshfegh, who heads FSRG. "Today, that information is more important than
ever. About 60 percent of the U.S. population is overweight or at risk for
AMPM is now the cornerstone of the FSRG's Dietary Intake Data Systeman overarching infrastructure of computer programs and databases that serves as the backbone for the federal government's annual national survey known as "What We Eat in America."
From Paper and Pen to Automation
From 1994 to 1998, the survey of food intake was conducted in person, by an interviewer using paper and pencil to record a respondent's replies using a three-step method. During one step, respondents were asked to recall, in chronological order, the foods they'd consumed the previous day.
Respondents use this two-
dimensional drawing to
estimate portion size.
Seven years ago, FSRG began
planning the transition from paper and pencil to computer-assisted interviewing
instruments. The group first identified key strengths and weaknesses of the old
method. They also talked with former interviewers to solicit feedback. From
there, several options were evaluated, based on in-depth interviews with
volunteers. The researchers learned that the respondents' ability to recall
dietary information might improve if they were not required to report foods
eaten in chronological order.
"With the new five-step system, we start by encouraging people to tell us about the foods they remembered eating the day before in any order they wish," says Moshfegh. "We wanted to take the burden of reporting in a specific order away from the respondents, so their minds could be free to reflect on the foods they'd actually eaten. At this point, a rapport is developing between the respondent and the interviewer."
The second step involves probing the respondent's mind for forgotten foods. Carefully crafted questions, embedded with word triggers and probes, ignite memories of potentially forgotten foods eaten. During the third step, answers already given are readdressed in the context of an "eating occasion," such as breakfast, snack, or lunch, as well as a time of day. For example, the interviewer will ask, "What would you call that eating occasion?"
Using serving-size aides,
nutritionist Grace Omolewa-
Tomobi, left, helps a
recall food portions.
The five-step system was designed so that respondents are more in control
during the first three steps. The fourth step is reserved for more difficult,
detail-oriented questions, carefully executed by the interviewer after having
developed a rapport, to increase the possibility of eliciting a thoughtful
response. The fifth step provides one last opportunity to remember foods that
In 1999, FSRG pilot-tested its new automated system by surveying 800 people, randomly chosen, nationwide. Those agreeing to participate were mailed visual aids for describing specific quantities of foods eaten. These included the USDA Food Model Booklet, measuring cups and spoons, and a ruler, to help respondents estimate the amounts of various foods eaten.
"The pilot study showed us that AMPM could be successfully used for collecting data over the telephone and that it could perform as well as, if not better than, the three-step method using paper and pencil," says Moshfegh.
Nutritionist Donna Rhodes,
left, prepares to measure
Ayanna Smith's heart rate
after vigorous exercise.
The Long Road to
Late last year, FSRG completed the data-collection phase of a large-scale
human research study designed to measure the effectiveness of AMPM. Preliminary
research findings show the method enabled the first 100 volunteers to recall
what they'd eaten to within 2 percent of the actual calories used.
The FSRG started planning the AMPM validation study at the same time it
started producing the automated instrument. "Gearing up to process 525
volunteers onsitein a way that would ensure scientific integrity with the
least possible disruption to the volunteers' lifestylestook considerable
time and resources," says Moshfegh. "It's the largest human research
study we've conducted here."
The researchers used a series of biochemical and physiological tests to support their ability to estimate the actual calories that volunteers consumed during the study and to assess other health indicators.
To estimate calories burned
during rest, exercise physiologist
David Paul measures gases
expelled by Ernie Goins in
Biological samples, including
blood, urine, saliva, and fat, were taken from volunteers. Tiny test tubes
called cryovials were used to store each volunteer's samples. "We used
about 52,000 cryovials for the entire study," says Moshfegh.
The researchers outfitted volunteers with a tiny motion detector worn around
the waist to measure total daily activity, which could be related to calories
burned. They measured the amount of oxygen volunteers consumed while breathing
under a large, Plexiglas canopy to determine calories burned during rest. And
they measured volunteers' heart rates to assess their fitness levels during
physical exercise. Each volunteer also consented to a full body scan to assess
body composition and bone density.
One of the most important metabolic indicators was measured by giving the volunteers a drink of water with two natural isotopes added. This "doubly labeled" water has slightly more mass than regular water, so it can be detected in body fluids by sensitive instruments as it's eliminated. The turnover rate of the special water allowed researchers to calculate how many calories each volunteer actually burned over the 2-week study period.
Keeping It Real
One of the group's goals was to replicate, as much as possible, the
food-intake survey experience in the real world. "I keep pretty busy, so I
don't always pay attention to what I eat," says Michael McMenamin, a study
participant. "When the interviewer took charge of the process, sometimes
she'd ask questions about a particular eating occasion. That would remind me of
a particular item I'd eaten earlier, which I'd forgotten to tell her. I found
that the questions led me along a path that allowed me to continue the flow of
the conversation. And so at times when I'd realize there was something I'd
skipped telling her, I could easily add it in."
Another participant, Robert Ingwersen, says he's generally conscientious
about the foods he eats and rarely has difficulty remembering them later.
"I usually don't do well on the phone, but because of the way the
interview was conducted, I was comfortable," he says.
The AMPM validation study has created a large database on diet, energy expenditure, weight status, body composition, physical activity, fitness, and biochemical indices of diet and health of the 525 adult participants. The study's large core of data may be used as the foundation for future diet and health studies. FSRG will continue analyzing the data over the next year.
A National Role
Nearly 50 years ago, Congress mandated that a continuing survey be conducted
periodically to collect statistical data about the current dietary intake and
health of people in the United States. That survey is called NHANES (National
Health and Nutrition Examination Survey), and it's conducted by the U.S.
Department of Health and Human Services.
In 2002, AMPM was first used to collect the dietary intake component of the
national survey. "FSRG not only produced the AMPM, but we are also
responsible for its implementation as the cornerstone for dietary intake
collection within NHANES," says Moshfegh.
After collection during the national survey, AMPM data are sent back to FSRG
for processing, analysis, and reporting. The resulting information is used by
various public and private groups as the basis for conducting in-depth studies.
Those analytical studies in turn fulfill specific health-related goals and
influence public policy to improve the health of the U.S. population, including
food assistance and education programs.
"With chronic diseases and other health conditions directly related to
nutrition and dietary intake, it's critical that we are able to accurately
assess diets," says Moshfegh. "It's also important so that we can
provide the right guidance and information to help Americans change their
eating habits to be more healthy. That ultimately will improve their quality of
life."By Rosalie Marion
Bliss, Agricultural Research Service Information Staff.
This research is part of Human Nutrition, an ARS National Program (#107)
described on the World Wide Web at www.nps.ars.usda.gov.
"Researchers Produce Innovation in Dietary Recall" was published in the June 2004 issue of Agricultural Research magazine.