Systematic errors in middle-aged women's estimates of energy intake: comparing three self-report measures to total energy expenditure from doubly labeled water.

PURPOSE: To evaluate energy intake (EI) derived from a food frequency questionnaire (FFQ), seven-day dietary recall (7DDR), and seven 24-hour dietary recall interviews (24HR) for reporting errors associated with social desirability and social approval.
METHODS: The FFQ and 7DDR were administered once before and once after a 14-day metabolic period during which total energy expenditure was determined using the doubly labeled water method (TEE(dlw)). Seven 24HR were conducted over the 14-day period. Data obtained from 80 healthy women (mean age = 49.1 years) were fit to linear regression models in which the EI estimates were the dependent variables and estimates of social desirability and social approval traits, body mass index [weight (kg)/ height (m)(2)], and TEE(dlw) were fit as independent variables.
RESULTS: indicated that in college-educated women there was an underestimate associated with social desirability on the FFQ (-42.24 kcal/day/point on the social desirability scale; 95% CI:-75.48, -9.00). For college-educated women with an average social desirability score ( approximately 17 points) this would equal an underestimate of 507 kcal/day compared to women with the minimum score (4 points). The 7DDR was associated with a differential effect of social approval when comparing by education; i.e., there was a difference of 36.35 kcal/day/point between the two groups (-14.69 in women with >/=college and 21.66 in women with <college) (95% CI: 10.25, 62.45).
CONCLUSIONS: Social desirability and social approval distort energy intake estimates from structured questionnaires, in a manner that appears to vary by educational status. Results observed have important implications for subject recruitment, data collection, and for methods of detection and control of biases in epidemiologic studies.