In the context of weight loss randomized trials and the clinical outcomes in our review, there are two considerations for describing control group interventions.
Firstly, in the context of interventions causing weight loss in control groups, in a systematic review and meta-regression, Waters and colleagues (1) found that control groups only receiving follow-up measurements lost 1kg less than control groups getting ‘usual care’ over a median period of 6 months. But Waters and colleagues were unable to determine which factors for control groups predicted greater weight loss.
In a second systematic review with meta-regression, Johns and colleagues (2) found that minimal control group interventions were associated with 1kg weight loss at 12 months. Intensity of control group interventions and additional weigh-ins independently predicted control group weight loss, but when both were modelled together neither was associated with weight change.
Details of the content of control group interventions (and weight loss interventions too) are often poorly provided. In our current NIHR funded REBALANCE project (3) we are attempting to predict weight loss in control groups and intervention groups by including coding of the 93 behaviour change techniques from the taxonomy (4). To do this properly requires additional information to that which authors put into the public domain. Trial materials that contain this information are difficult to obtain. For example, only one third of the authors we contacted in REBALANCE provided us with information to allow us to accurately code control group intereventions.
Secondly, because behavioural weight loss trials are unblinded, care given outside the trial may differ between intervention and control arms. These differences are even less likely to be described than trial procedures. This may have particular bearing on the cardiovascular mortality and events in our review. In the largest trial in our review, the Look AHEAD trial, (5) the investigators commented that the increased use of statins in the control group compared with the intervention group may have lessened differences between the groups for cardiovascular events.
Thus detailing and classifying control group interventions for the purposes of our review carries unique challenges, which we are trying to address in our REBALANCE project.
References
(1) Waters L, St George A, Chey T, Bauman A. Weight change in control group participants in behavioural weight loss interventions: a systematic review and meta-regression study. BMC Med Res Methodol 2012;12:120
(2) Johns DJ, Hartmann-Boyce J, Jebb SA, Aveyard P, on behalf of the Behavioural Weight Management Review Group. Weight change among people randomized to minimal intervention control groups in weight loss trials. Obesity 2016;24:772-780.
(3) (REBALANCE) REview of Behaviour And Lifestyle interventions for severe obesity: AN evidenCE synthesis. https://www.journalslibrary.nihr.ac.uk/programmes/hta/150904/#/ (accessed 17/11/2017).
(4) Michie S, Richardson M, Johnston M, Abraham, Francis J, Hardeman W, et al. The behavior change techniques taxonomy (v1) of 93 hierarchically clustered techniques: building an international consensus for the reporting of behaviour change interventions. Ann Behav Med 2013;46:81-95.
(5) Look AHEAD Research Group. Cardiovascular effects of intensive lifestyle intervention in type 2 diabetes. N Engl J Med 2013;369:145-54 [Erratum in: N Engl J Med 2014;370:1866.].
Competing interests:
No competing interests
22 November 2017
Alison Avenell
Professor
Chenhan Ma, Mark Bolland (University of Auckland, New Zealand), Jemma Hudson, Fiona Stewart, Clare Robertson, Pawana Sharma, Cynthia Fraser, Graeme MacLennan
University of Aberdeen
Health Services Research Unit, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
Rapid Response:
Authors' reply to Michael D Hopkinson
We thank you for your interesting question.
In the context of weight loss randomized trials and the clinical outcomes in our review, there are two considerations for describing control group interventions.
Firstly, in the context of interventions causing weight loss in control groups, in a systematic review and meta-regression, Waters and colleagues (1) found that control groups only receiving follow-up measurements lost 1kg less than control groups getting ‘usual care’ over a median period of 6 months. But Waters and colleagues were unable to determine which factors for control groups predicted greater weight loss.
In a second systematic review with meta-regression, Johns and colleagues (2) found that minimal control group interventions were associated with 1kg weight loss at 12 months. Intensity of control group interventions and additional weigh-ins independently predicted control group weight loss, but when both were modelled together neither was associated with weight change.
Details of the content of control group interventions (and weight loss interventions too) are often poorly provided. In our current NIHR funded REBALANCE project (3) we are attempting to predict weight loss in control groups and intervention groups by including coding of the 93 behaviour change techniques from the taxonomy (4). To do this properly requires additional information to that which authors put into the public domain. Trial materials that contain this information are difficult to obtain. For example, only one third of the authors we contacted in REBALANCE provided us with information to allow us to accurately code control group intereventions.
Secondly, because behavioural weight loss trials are unblinded, care given outside the trial may differ between intervention and control arms. These differences are even less likely to be described than trial procedures. This may have particular bearing on the cardiovascular mortality and events in our review. In the largest trial in our review, the Look AHEAD trial, (5) the investigators commented that the increased use of statins in the control group compared with the intervention group may have lessened differences between the groups for cardiovascular events.
Thus detailing and classifying control group interventions for the purposes of our review carries unique challenges, which we are trying to address in our REBALANCE project.
References
(1) Waters L, St George A, Chey T, Bauman A. Weight change in control group participants in behavioural weight loss interventions: a systematic review and meta-regression study. BMC Med Res Methodol 2012;12:120
(2) Johns DJ, Hartmann-Boyce J, Jebb SA, Aveyard P, on behalf of the Behavioural Weight Management Review Group. Weight change among people randomized to minimal intervention control groups in weight loss trials. Obesity 2016;24:772-780.
(3) (REBALANCE) REview of Behaviour And Lifestyle interventions for severe obesity: AN evidenCE synthesis. https://www.journalslibrary.nihr.ac.uk/programmes/hta/150904/#/ (accessed 17/11/2017).
(4) Michie S, Richardson M, Johnston M, Abraham, Francis J, Hardeman W, et al. The behavior change techniques taxonomy (v1) of 93 hierarchically clustered techniques: building an international consensus for the reporting of behaviour change interventions. Ann Behav Med 2013;46:81-95.
(5) Look AHEAD Research Group. Cardiovascular effects of intensive lifestyle intervention in type 2 diabetes. N Engl J Med 2013;369:145-54 [Erratum in: N Engl J Med 2014;370:1866.].
Competing interests: No competing interests