This study compared self-reported television (TV)-viewing time with an objective measure obtained by an electronic TV monitor. As part of a larger study, 40 overweight and obese adults (BMI: 31.7 +/- 5.4 kg/m(2); 53% obese; mean age 41.4 +/- 13.0) self-reported TV-viewing time at study entry as the response to the question, "How many hours do you watch TV per day, on average?" Objective TV-viewing time was measured in min/day over 3 weeks/subject using electronic monitors. Self-reported viewing time was 4.3 +/- 1.3 h/day (mean +/- s.d.) (range: 3.0-8.0 h/day) vs. 4.9 +/- 2.6 h/day (0.8-13.3 h/day) recorded by the electronic TV monitor. Subjects underestimated their viewing time by 0.6 +/- 2.3 h/day (95% confidence interval = -1.34, 0.13), or 4.3 h/week. Slightly over half of the subjects (58%) underestimated their viewing time; 47.5% were within 1 h/day, and 72.5% were within 2 h/day of self-reported viewing time. Large errors were rare in this group, suggesting that a simple self-report measure of TV time may be useful for characterizing viewing behavior, although objective measurement adds precision that may be useful in certain settings.
Trial registration: ClinicalTrials.gov NCT00622050.