Purpose Sample Data Collection Period Study Design Measurements Doubly-Labeled Water Method Study Status

Purpose – Use biomarkers of energy and protein intake to validate the AMPM  

Sample – 524 healthy volunteers from the Washington DC area:

• 30-69 years of age, equal numbers of males and females
   
• BMI range of 18-44 kg/m²
   
• Weight stable
   
• No medications known to affect food intake or water balance

Data Collection Period – July 2002 to September 2003

Study Design – Each volunteer entered the study for a 14-day period, and data were collected during 4 visits to the Beltsville Human Nutrition Research Center plus 3 telephone contacts. During the study period, participants were interviewed three times using the AMPM, and asked to report all foods and beverages eaten the previous day. These food recalls were conducted four to five days apart. The first interview was conducted in-person and subsequent recalls were conducted by telephone. Over the 15 months of the study, interviews were conducted on every day of the week and during all seasons of the year. Because the AMPM is the instrument used to collect dietary data in What We Eat in America, the dietary intake interview component of the National Health and Nutrition Examination Survey (NHANES), the environment in which participants were interviewed replicated that used for the NHANES dietary interview to the extent possible.

Measurements:

• Total energy expenditure by the doubly labeled water method
   
• 24-hour urinary nitrogen excretion as a biomarker for protein intake
   
• Resting energy expenditure
   
• Physical activity measured with the MTI Actigraph worn for 14 days
   
• Height, weight, waist and hip circumference
   
• Body composition and bone density measured by dual energy x-ray absorptiometry
   
• Blood pressure
   
• Fasting blood and adipose tissue samples
   
• Questionnaires on physical activity, dietary supplement use, and psychosocial factors associated with eating behavior
   
• Physical fitness measured on a stationary bicycle

Doubly Labeled Water Method – The doubly labeled water method was used to validate energy intake. It provides an accurate measure of total daily energy expenditure. When individuals are weight stable (not gaining or losing weight), energy expenditure and energy intake are equal. Thus, the energy expenditure estimates that the method provides serve as an excellent biomarker for energy intake.

On their first visit to the study center, participants drank a dose of doubly labeled water and then collected urine samples daily over the 14-day study period. Doubly labeled water contains a higher concentration than usual of deuterium and oxygen-18, which are naturally-occurring stable isotopes of hydrogen and oxygen. The rates at which these isotopes are excreted in urine can be measured and used to calculate total daily energy expenditure.

Study Status:

• Biological samples will continue to be analyzed through 2005.
   
• Data from the study will be used to:
      - Identify the magnitude of reporting error in dietary intakes collected
        with the AMPM.
      - Define socio-demographic and psychosocial characteristics associated
        with misreporting of energy and protein intake.
      - Identify differences in food and nutrient intakes of acceptable versus
        poor reporters.
      - See how AMPM memory cues and portion size estimation aids affect
        accuracy.
   
• Preliminary results based on the first 100 subjects have been presented in poster presentations and reports as follows:
      - Rhodes DG, Moshfegh A, Cleveland L, Murayi T, Baer D, Sebastian R,
        and Perloff B. (2004).  Accuracy of 24 hour dietary recalls: Preliminary
        results from USDA AMPM Validation Study. FASEB J 18(4): A111.
      - Moshfegh AJ, Cleveland LE, Baer DJ, Sebastian RS, Rhodes DG,
        and Perloff BP. (2003). Accuracy of Americans reporting dietary intakes:
        Results from cohort 1 of the USDA Doubly Labeled Water Study.
        J Am Diet Assoc 103(9):A-23.
      - Bliss, R.M. (2004). Researchers produce innovation in dietary recall.
        Agric Res 52(6):10-12.