“CATCH-IT Reports” are Critically Appraised Topics in Communication, Health Informatics, and Technology, discussing recently published ehealth research. We hope these reports will draw attention to important work published in journals, provide a platform for discussion around results and methodological issues in eHealth research, and help to develop a framework for evidence-based eHealth. CATCH-IT Reports arise from “journal club” - like sessions founded in February 2003 by Gunther Eysenbach.

Sunday, November 22, 2009

CATCH-IT Draft: Web-based Weigt Loss in Primary Care: A RCT

CATCH-IT abstract: click here


Obesity rates have been rising in Canada and other countries around the world.(1) The annual cost of obesity in Canada has been estimated at $2 billion, or 2.4% of total health care expenditures.(2) Behaviour therapy can significantly enhance comprehensive weight loss strategies but access to lifestyle interventions are limited by costs and availability of counselling services. Bennett et al.(3) present a low cost web-based intervention with the potential of reaching a large number of individuals.


The objective of the study was to evaluate the short-term (12-week) efficacy of a web-based behavioral intervention in primary care patients with obesity (BMI 30 to 40 kg/m2) and hypertension.


A total of 101 obese, hypertensive patients were randomized to receive either the web-based intervention (n=51) or usual care (n=50). Intervention participants had access to a comprehensive weight loss website for 3 months, and four counselling sessions (two in-person and two telephone). The health coach was a registered dietician trained to use principles of motivational interviewing. Counselling was provided on assigned obesogenic behavior goals only, which were determined at the start of the intervention. At week 6, participants could select new goals. The primary purpose of the website was to facilitate daily self-monitoring of adherence to behavior change goals. Usual care was defined as standard care offered by the outpatient clinic, plus the “Aim for a Healthy Weight” document published by the National Heart Lung and Blood Institute.(4)

At baseline, and at the 3 month follow-up, participants completed a web-based survey followed by anthropometric measures and blood pressure assessments. Participants were offered $25 for attending each assessment.


Primary outcome: Intervention participants lost (-2.281 kg +/- 3.21) compared with a weight gain of (0.28 +/- 1.87 kg) in the usual care group; mean difference -2.56 kg (95% CI -3.60, -1.53). Intervention participants lost a greater percentage of baseline body weight (-2.6% +/- 3.3%) than usual care participants (0.39% +/- 2.16%); mean difference of -3.04% (95% -4.26, -1.83). About a quarter of intervention participants (25.6%) lost >5% of their initial body weight at 12-week compared to none in the usual care group.

Secondary outcomes: A reduction in BMI was observed among the intervention group (-0.94 +/- 1.16 kg/m2) versus usual care group (0.13 +/- 0.75 kg/m2); mean difference of -1.07 kg/m2 (95% CI -1.49, -0.64). No statistically significant differences were found for waist circumference, systolic blood pressure, and diastolic blood pressure.

Participants meeting the login goal (3 times per week) for at least 50% of study period (>=6 weeks) had greater weight loss (-3.30 +/- 3.78 kg) than those who met the login goal for fewer than 6 weeks (-0.42 +/- 1.78 kg); mean difference: -2.88 kg (95% CI -1.56, -4.60). Those who met the login goal for 10 weeks (83% of study weeks) demonstrated much greater weight loss (-4.50 +/- 3.29 kg) than those who did not (-0.60 +/- 1.87); mean difference: -3.90 kg; (95% CI -2.43, -5.36).

No association was found between participation in four coaching sessions and weight loss.


Bennett et al. reported short term weight loss of -2.25kg +/- 3.21 (intent-to-treat) using a web based intervention. While this addresses the primary hypothesis that participants randomized to the web-based intervention would demonstrate greater weight losses compared to usual care, a weight loss of 2.25kg in a 101.0 kg individual (mean weight of intervention participant) represents a 2.2% loss of body weight, which may be of limited clinical significance.
The authors also noted the small sample size as a limitation. Further to this, the sample size calculations used to determine the number of participants needed to detect at least a 5 kg mean weight difference, falls short of the recommended 10% weight loss target for obese individuals through a combination of diet, physical activity, and behaviour therapy.(5,6)

Also, loss of 2.2% body weight is somewhat lower that the 5% weight loss reported by other internet intervention studies.(5) The authors noted this as a limitation of their intervention, that the smaller observed weight loss may be a result of the lack of dietary restrictions in their study since the intervention was created to produce “an energy deficit sufficient to produce weight loss exclusively through the modification of routine obesogenic lifestyle behaviors” as dietary restrictions would be necessary for greater magnitude of weight loss. However, the Canadian Obesity Guidelines recommends diet and physician activity as the first line treat of obesity, where behavior interventions are considered as an adjunct to other interventions.(2) Literature to support the use of behaviour modification alone for obese patients is lacking. It was also not clear why the obese patients were selected in the study, as opposed to weigh loss for overweight individuals, where lifestyle interventions alone may be more common.

The short length of the study was unusual, given that long-term weight loss is the main challenge in obesity management. The 13 week trial period is shorted than study periods reported by other trials,(5,6) and may have contributed to the lower reported efficacy.

On the other hand, the short length may have contributed to the higher participant retention (84% intervention participants completed the study, 84% usual care participants completed the study and 84% of the total number of participants completed the study). The authors suggest that the health coach was the key factor in their low attrition rate, noting that Rothert et al. (7) found much lower rates of attrition (16%) in their web based intervention without coach support. Perhaps this was influeced by “push” factors described by Eisenbach (8) where research assistants (or health coach) contacting participants can lower attrition rate. As such, it is not clear whether implementation of this tool without health coach, as suggested by the authors, may result in a lower attrition rate. Or, could the high attrition rate found by the authors be due to the web tool itself? The short, simple, obesogenic behaviour change goals ("Walk 10,000 steps every day," "Watch 2 h or less of TV every day," "Avoid sugar-sweetened beverages," "Avoid fast food," "Eat breakfast every day," and "No late night meals and snacks") may represent the “shorter interventions” that Christensen (9) argues could be the primary role of the internet in disease prevention instead of delivery of lengthy therapy that requires hours of online work. Details of the web intervention were limited and the theoretical model used in the study was not defined. There was a lack of information in the literature on the iOTA (interactive weight loss approach). In a recent correspondence to the author, Bennett indicated that more details on iOTA will be available shortly. His website is http://bennettlab.org.

According to the authors, the intervention was developed to overcome the challenge of long term adherence, since adherence to behaviour change strategies often wanes over time. But the percentage of participants who met the login goal (3 times per week) also decreased over the course of the study (78% at week 1 versus 43.1% at 12 weeks). The use of two raffles for $50 gift certificates was an interesting method to encourage participant logins, but it is difficult to assess the actual impact of these logins as noted by the authors.

In terms of future research, it would be interesting to compare the web based intervention with other weight loss interventions (e.g. paper based self monitoring tool, or web intervention without the health coach). Although comparison with “usual care” may be common practice in randomized controlled trials, a “head-to-head” trial in pharmaceutical studies with “me-too” drugs may provide a bigger contribution to knowledge. As such, providing an intervention in the alternative group may also address the lack of blinding of the participants to some degree. Blinding of the research assistants only without blinding participants and primary care providers, may introduce some bias to the data away from the null, potentially overestimating the magnitude of the intervention.

The web intervention included many interesting features such as the display of the “average performance for other program participants,” regular updates to behavioural skills needed to adhere to obesogenic behaviour change goals, social networking forum, recipes. A comparison of the web based intervention with a paper based monitoring tool would be very interesting as these features are enabled by internet tools which could not be easily achieved with a paper based self monitoring tool.

A couple of additional minor comments: Some of the references noted in the paper do not support the text. For example, on page 2, the paper states that “research staff subsequently collected anthropometric measures and blood pressure using established procedures (reference 20).” However, reference 20 refers to a 24 page survey (NHANES food questionnaire).(10)

On Table 1 (page 2), intervention participants (n = 51) had a higher body weight (101.0 kg +/- 15.4 kg) than usual care participants (n = 50) who had s body weight of (97.3 +/- 10.9kg). It is unclear how the body weight of all participants (n=101) was reported as (97.3 kg +/- 10.9), the same weight as usual care participants, but includes the intervention group had a higher mean weight.

In summary, despite the issues noted above, study was well designed. The paper included most items on the CONSORT(11,12) and STARE-HI(13) checklists. My thoughts are that perhaps the trial was an exploratory attempt to pilot the web-based intervention for a more comprehensive study, although this was not explicitly mentioned. It appears that the authors have already begun other trials using their iOTA approach (see website).


1. In the usual care group, what was standard care? How many visits did the usual care group make to the primary care provider for weight reduction?
2. Of the 124 ineligible participants, what were the reasons for ineligibility?
3. What was the web based survey completed by participants at baseline and at 3 months follow-up? Was the NHANES food questionnaire used as the web based survey? What were the results of the survey?
4. Table 3 (page 4) excluded the one participant who did not login once. Given that the range of logins from week 1 to week 12 includes “0”, why was this data omitted?
5. Intervention participants received “two 20-min motivational coaching sessions in person (baseline and week 6), and two, 20-min biweekly sessions via telephone (week 3 and 9)”. Were there biweekly telephone coaching sessions in addition to the two telephone sessions at week 3 and week 9? What was the impact of the “message feature that allowed for direct communication with the coach”? Was there extended access to the health coach beyond the four sessions throughout the 12 week study period?
6. With regards to the web-based intervention, what was being tracked by the web-based intervention (number of times eat out, number of stairs walked)? How many minutes on average did each session take? What behaviour skills were presented on the website and updated biweekly? What was the impact of the social networking forum?


1. OECD Health Data 2009: How Does Canada Compare. http://www.oecd.org/dataoecd/46/33/38979719.pdf
2. Lau DCW, Douketis JD, Morrison KM, Hramiak IM, Sharma AM, Canadian clinical practice guidelines on the management and prevention of obesity in adults and children. CMAJ 2007;176(8 suppl):Online-1–117 www.cmaj.ca/cgi/content/full/176/8/S1/DC1
3. Bennett G Bennett GG, Herring SJ, Puleo E, Stein EK, Emmons KM and Gillman MW. Web-based Weight Loss in Primary Care: A Randomized Controlled Trial. Obesity (2009) Advance online publication, 20 August 2009. DOI:10.1038/oby.2009.242
4. Wadden TA, Butryn ML, Wilson C. Lifestyle modification for the management of obesity. Gastroenterology. 2007 May;132(6):2226-38.
5. Sarwer DB, von Sydow Green A, Vetter ML, Wadden TA. Behavior therapy for obesity: where are we now? Curr Opin Endocrinol Diabetes Obes. 2009 Oct;16(5):347-52. DOI: 10.1097/MED.0b013e32832f5a79
6. M. Neve, P. J. Morgan, P. R. Jones and C. E. Collins. Effectiveness of web-based interventions in achieving weight loss and weight loss maintenance in overweight and obese adults: a systematic review with meta-analysis. Obesity Reviews. 2009 Sep 14 DOI: 10.1111/j.1467-789X.2009.00646.x
7. Rothert K, Strecher VJ, Doyle LA et al. Web-based weight management programs in an integrated health care setting: a randomized, controlled trial. Obesity (Silver Spring) 2006;14:266–272.
8. Eysenbach Gunther. The Law of Attrition. J Med Internet Res. 2005;7(1):e11. doi: 10.2196/jmir.7.1.e11. http://www.jmir.org/2005/1/e11/v7e11
9. Christensen H, Ma A. The Law of Attrition Revisited. (J Med Internet Res 2006;8(3):e20) doi:10.2196/jmir.8.3.e20. http://www.jmir.org/2006/3/e20/
10. National Heart, Lung, and Blood Institute, National Institutes of Health. Aim for a Healthy Weight. Washington DC: US Department of Health and Human Services, 2005. http://www.nhlbi.nih.gov/health/public/heart/obesity/aim_hwt.pdf
11. Moher D, Schulz KF, Altman DG for the CONSORT Group. The CONSORT Statement: Revised Recommendations for Improving the Quality of Reports of Parallel-Group Randomized Trials. Ann Intern Med. 2001;134:657-662. (http://www.consort-statement.org)
12. Altman DG, Schulz KF, Moher D, Egger M, Davidoff F, Elbourne D, G√łtzsche PC, Lang T for the CONSORT Group. The Revised CONSORT Statement for Reporting Randomized Trials: Explanation and Elaboration. Ann Intern Med. 2001;134:663-694. (http://www.consort-statement.org)
13. Talmon J, Ammenwerth E, Brender J, de Keizer N, Nykänen P, Rigby M. STARE-HI--Statement on reporting of evaluation studies in Health Informatics. Int J Med Inform. 2009 Jan;78(1):1-9.


  1. One point for consideration, there are no statistically significant values reported (related to outcomes) which might suggest the null hypothesis is supported, and that the intervention is no different than usual care. The manner in which the authors report outcomes, e.g. "greater weight loss was observed", along with statements that weight loss interventions can be successfully offered in primary care settings (based on these results) are difficult to support if you fail to reject the null hypothesis. At the very least, it may be helpful to have the authors offer more information about the outcomes measures in relation to this.

  2. Again: Can you (and everybody else) please add the complete bibliographic citation of the study under discussion at the top of the report.

    You have too many typos and some awkward sentences in your report, e.g. "It is unclear how the body weight of all participants (n=101) was reported as (97.3 kg +/- 10.9), the same weight as usual care participants, but includes the intervention group had a higher mean weight.". You are onto something here - namely that some of the numbers reported in the table clearly make no sense, which for me is always alarming. Unfortunately, you bury this observation at the end of your report in a grammatically botched sentence.

    I am not sure if I would agree with the statement on this being an "exploratory" study. RCTs are rarely exploratory.

    Laure: I would interpret the result that the "mean difference [is] -2.56 kg (95% CI -3.60, -1.53)" as an indication that there is a statistically significant difference (otherwise the upper end of the CI would be >0).

  3. My apologies, the primary and secondary outcomes are specifically reported related to finding differences and not finding differences, along with appropriate confidence intervals. Please disregard my earlier post.

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  5. Hi Claudia,

    You may also want to add the folllowing comment:

    Authors used 6 weeks and 10 weeks as cut off points for categorization of participants study periods. These two cut points are kind of arbitrary and it not clear whether small changes in these cut points would maintain the significance findings or not. A better approach would be correlating the amount and percentages of weight loss with percentages of study period using simple correlation statistics. A positive and significant correlation would support their findings in a way that a higher study participation would result in a higher weight loss. Thank you.

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