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Longitudinal accuracy of web-based self-reported weights: results from the Hopkins POWER Trial.

Jerome GJ, Dalcin A, Coughlin JW, Fitzpatrick S, Wang NY, Durkin N, Yeh HC, Charleston J, Pozefsky T, Daumit GL, Clark JM, Louis TA, Appel LJ - J. Med. Internet Res. (2014)

Bottom Line: Research staff used a standard protocol to measure weight in the clinic.The absolute value of the differences (absolute difference) describes the overall accuracy.The average absolute difference also increased from 6 months (mean 0.7 kg, SD 0.8 kg) to 24 months (mean 1.3, SD 1.8 kg; P<.001).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Kinesiology, Towson University, Towson, MD, United States. gjerome@towson.edu.

ABSTRACT

Background: Websites and phone apps are increasingly used to track weights during weight loss interventions, yet the longitudinal accuracy of these self-reported weights is uncertain.

Objective: Our goal was to compare the longitudinal accuracy of self-reported weights entered online during the course of a randomized weight loss trial to measurements taken in the clinic. We aimed to determine if accuracy of self-reported weight is associated with weight loss and to determine the extent of misclassification in achieving 5% weight loss when using self-reported compared to clinic weights.

Methods: This study examined the accuracy of self-reported weights recorded online among intervention participants in the Hopkins Practice-Based Opportunities for Weight Reduction (POWER) trial, a randomized trial examining the effectiveness of two lifestyle-based weight loss interventions compared to a control group among obese adult patients with at least one cardiovascular risk factor. One treatment group was offered telephonic coaching and the other group was offered in-person individual coaching and group sessions. All intervention participants (n=277) received a digital scale and were asked to track their weight weekly on a study website. Research staff used a standard protocol to measure weight in the clinic. Differences (self-reported weight - clinic weight) indicate if self-report under (-) or over (+) estimated clinic weight using the self-reported weight that was closest in time to the clinic weight and was within a window ranging from the day of the clinic visit to 7 days before the 6-month (n=225) and 24-month (n=191) clinic visits. The absolute value of the differences (absolute difference) describes the overall accuracy.

Results: Underestimation of self-reported weights increased significantly from 6 months (mean -0.5 kg, SD 1.0 kg) to 24 months (mean -1.1 kg, SD 2.0 kg; P=.002). The average absolute difference also increased from 6 months (mean 0.7 kg, SD 0.8 kg) to 24 months (mean 1.3, SD 1.8 kg; P<.001). Participants who achieved the study weight loss goal at 24 months (based on clinic weights) had lower absolute differences (P=.01) compared to those who did not meet this goal. At 24 months, there was 9% misclassification of weight loss goal success when using self-reported weight compared to clinic weight as an outcome. At 24 months, those with self-reported weights (n=191) had three times the weight loss compared to those (n=73) without self-reported weights (P<.001).

Conclusions: Underestimation of weight increased over time and was associated with less weight loss. In addition to intervention adherence, weight loss programs should emphasize accuracy in self-reporting.

Trial registration: ClinicalTrials.gov: NCT00783315; http://clinicaltrials.gov/show/NCT00783315 (Archived by WebCite at http://www.webcitation.org/6R4gDAK5K).

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Differences in weights (self-reported – clinic) by the average of the two weights at 24 months.
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figure2: Differences in weights (self-reported – clinic) by the average of the two weights at 24 months.

Mentions: Figure 2 is a Bland Altman Plot comparing self-reported and clinic weights at 24 months. A majority of the extreme differences between self-reported and clinic weights occur between 80 kg and 130 kg. The intraclass correlation comparing self-reported and clinic weights at 24 months was .99.


Longitudinal accuracy of web-based self-reported weights: results from the Hopkins POWER Trial.

Jerome GJ, Dalcin A, Coughlin JW, Fitzpatrick S, Wang NY, Durkin N, Yeh HC, Charleston J, Pozefsky T, Daumit GL, Clark JM, Louis TA, Appel LJ - J. Med. Internet Res. (2014)

Differences in weights (self-reported – clinic) by the average of the two weights at 24 months.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4129117&req=5

figure2: Differences in weights (self-reported – clinic) by the average of the two weights at 24 months.
Mentions: Figure 2 is a Bland Altman Plot comparing self-reported and clinic weights at 24 months. A majority of the extreme differences between self-reported and clinic weights occur between 80 kg and 130 kg. The intraclass correlation comparing self-reported and clinic weights at 24 months was .99.

Bottom Line: Research staff used a standard protocol to measure weight in the clinic.The absolute value of the differences (absolute difference) describes the overall accuracy.The average absolute difference also increased from 6 months (mean 0.7 kg, SD 0.8 kg) to 24 months (mean 1.3, SD 1.8 kg; P<.001).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Kinesiology, Towson University, Towson, MD, United States. gjerome@towson.edu.

ABSTRACT

Background: Websites and phone apps are increasingly used to track weights during weight loss interventions, yet the longitudinal accuracy of these self-reported weights is uncertain.

Objective: Our goal was to compare the longitudinal accuracy of self-reported weights entered online during the course of a randomized weight loss trial to measurements taken in the clinic. We aimed to determine if accuracy of self-reported weight is associated with weight loss and to determine the extent of misclassification in achieving 5% weight loss when using self-reported compared to clinic weights.

Methods: This study examined the accuracy of self-reported weights recorded online among intervention participants in the Hopkins Practice-Based Opportunities for Weight Reduction (POWER) trial, a randomized trial examining the effectiveness of two lifestyle-based weight loss interventions compared to a control group among obese adult patients with at least one cardiovascular risk factor. One treatment group was offered telephonic coaching and the other group was offered in-person individual coaching and group sessions. All intervention participants (n=277) received a digital scale and were asked to track their weight weekly on a study website. Research staff used a standard protocol to measure weight in the clinic. Differences (self-reported weight - clinic weight) indicate if self-report under (-) or over (+) estimated clinic weight using the self-reported weight that was closest in time to the clinic weight and was within a window ranging from the day of the clinic visit to 7 days before the 6-month (n=225) and 24-month (n=191) clinic visits. The absolute value of the differences (absolute difference) describes the overall accuracy.

Results: Underestimation of self-reported weights increased significantly from 6 months (mean -0.5 kg, SD 1.0 kg) to 24 months (mean -1.1 kg, SD 2.0 kg; P=.002). The average absolute difference also increased from 6 months (mean 0.7 kg, SD 0.8 kg) to 24 months (mean 1.3, SD 1.8 kg; P<.001). Participants who achieved the study weight loss goal at 24 months (based on clinic weights) had lower absolute differences (P=.01) compared to those who did not meet this goal. At 24 months, there was 9% misclassification of weight loss goal success when using self-reported weight compared to clinic weight as an outcome. At 24 months, those with self-reported weights (n=191) had three times the weight loss compared to those (n=73) without self-reported weights (P<.001).

Conclusions: Underestimation of weight increased over time and was associated with less weight loss. In addition to intervention adherence, weight loss programs should emphasize accuracy in self-reporting.

Trial registration: ClinicalTrials.gov: NCT00783315; http://clinicaltrials.gov/show/NCT00783315 (Archived by WebCite at http://www.webcitation.org/6R4gDAK5K).

Show MeSH
Related in: MedlinePlus