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A women-centred, tailored SMS-delivered multi-component intervention for weight loss

A women-centred tailored SMS-delivered multi-component intervention for weight loss and maintenance of weight loss in the postpartum period: intervention adaption and pilot RCT


  • To assess and refine the txt2stop logic model for weight loss and maintenance of weight loss. Txt 2 stop is an automated smoking cessation programme delivered via mobile phone text messaging by C Free, which is effective, cost-effective and has been implemented across the NHS.
  • To adapt the SMS intervention for use in the context of weight loss and maintenance of weight loss in postpartum women.
  • To develop the protocol for a pilot trial of the SMS intervention.
  • To conduct a pilot RCT to: trial recruitment and randomisation strategies; examine fidelity of implementation and acceptability of the intervention; identify valid and PPI acceptable research instruments to be used in a full trial; provide variability data on the primary endpoints (weight loss and maintenance of weight loss) on which to base a formal power calculation for a definitive trial; and, to assess outcome data collection processes.
  • To assess pilot data in relation to pre-defined stop/go criteria for a full trial
  • Based on the data from the pilot study, if proceeding to a full trial is warranted: To develop a protocol for a multicentre RCT to evaluate the effectiveness of a tailored SMS-based intervention for weight loss and maintenance of weight loss in postpartum women.


Obesity has nearly doubled worldwide since 1980 and this has implications for maternal health.  Excessive gestational weight gain and postpartum weight retention are established predictors of long term obesity.  Systematic review evidence and NICE guidance both highlight gaps in knowledge about effective and appropriate weight management interventions in women during the postpartum period.

Phase 1: Intervention adaptation of the text2stop text automated messages and development of protocol for the pilot trial: This used an iterative process conducted in conjunction with postpartum women in order to develop a woman-centred, tailored SMS intervention that facilitates a self-directed approach to behaviour change. 

Phase 2: (in progress).  The pilot study is a parallel group RCT conducted at one site (Belfast). Eligibility: women from birth until 2 years postnatal, uniparous or multiparous, with postpartum BMI >25 kg/m2.

The intervention group will receive the SMS intervention; the control group will be an ‘active control’ and will receive SMS messages related to child care and child development.

The 12 month pilot intervention (sufficient to allow examination of weight loss as well as a 3-6 month ‘maintenance’ period for most participants) will have data collection taking place at 3, 6, and 12 months.


The primary outcome of the pilot trial will be to provide a decision regarding the feasibility of proceeding to a multi-centre RCT to fully test the intervention. This decision will be based on an assessment of quantitative and qualitative data. Stop/go criteria for proceeding to a full trial are based on acceptability and feasibility outcomes:

  • Acceptability of the intervention and ‘active control’ (satisfaction rating, qualitative views)
  • Feasibility of recruitment – successful recruitment - at least 80% of pilot study target
  • Retention rate consistent with other weight loss interventions in this target group, i.e. at least 65% in intervention group and 60% in control group (2,3,4)
  • Evidence of positive indicative effects - change in anthropometric measures over time

In addition questionnaires will be used to collect 4-day food diary to assess dietary intake, other lifestyle behaviours - physical activity, sedentary behaviour, smoking, alcohol, measures to inform future trial economic analysis, theory-based mediators of behaviour change including self efficacy, motivation, social support, self-regulation, habit formation  and child-related outcomes - infant feeding (breastfeeding behaviour and weaning) and growth.  A process evaluation using qualitative interviews will seek women’s experiences of being in the pilot trial and fidelity of the SMS intervention delivery will be assessed.

Principal Investigator: The Queen's University of Belfast

NMAHP Research Unit Collaborators: Professor Pat Hoddinott

External Collaborators: Anderson A - University of Dundee, Cardwell C - The Queen's University of Belfast, Dombrowski S - University of Stirling, Free C - London School of Hygiene & Tropical Medicine, Holmes V - The Queen's University of Belfast, Kee F - The Queen's University of Belfast, McIntosh E - University of Glasgow, Woodside J - The Queen's University of Belfast, Young I - The Queen's University of Belfast.

Funder:  NIHR

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