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Principal Investigator
Susan Jebb

1 June 2016 to 31 August 2017

Project No: 329

Funding round: FR 11

Susan Jebb and Amanda Daley

Pregnancy and the postnatal period are vulnerable life stages for gaining excess weight.  Many women report pregnancy as the critical point for the onset of later weight problems (1-2) which can significantly increase the risk of obesity and serious chronic diseases including type 2 diabetes, heart disease and cancer (3-4).  The postnatal period is characterised not only by weight retention, but also by susceptibility to further weight gain (5).  The NHS costs attributable to being overweight and obese are projected to reach £9.7 billion by 2050 (6).  It is estimated that at six weeks postnatally two thirds of women weigh more than their pre-pregnancy weight and by one year about 25% retain more than 4 kg of weight gained during pregnancy (7-8). There is an association between postnatal weight retention and poor mental health which is known to have negative consequences for the development of the infant and on the family as a whole (9-10). There is a need therefore to intervene routinely and early in the postnatal period, to help women to manage their excess weight after having a baby to minimise the long-term health risks.  Intervention may also have additional benefits by reducing weight at the start of subsequent pregnancies.

Current evidence and why the research is needed now

Systematic reviews have reported that most trials in this population have recruited small samples and/or tested interventions that have not been embedded within the public health system and several systematic reviews have also identified the need for high quality trials on how to best help women to lose weight after having a baby(11-15).  Within these reviews the vast majority of studies have evaluated intensive physical activity and/or diet based interventions delivered by specialists.  These types of interventions cannot be delivered to all the 820,000 women who give birth each year in the UK, 533,000 of whom will be overweight(16). We expect our approach to result in a smaller effect than for intensive interventions but because of its widespread applicability and scalability, to have a larger population level impact.  Whilst the many systematic reviews to date have all had different study inclusion and exclusion criteria, they have concluded that there are insufficient high quality trials to judge the effectiveness of interventions to promote healthy weight loss after having a baby.  Some reviews have noted that the vast majority of RCTs have been conducted outside the UK in predominately advantaged women.  

Self monitoring and self management of weight

Trials of self management interventions for weight loss can inform our knowledge about what types of self-directed weight loss strategies are most effective and which might be usefully highlighted to the public as a scalable, low cost public health intervention.  One such intervention that has shown promise in helping people manage their weight is regular weighing, to check progress against a target, a form of self monitoring.  The potential efficacy of regular weighing (either by the individual or someone else) has been based on the principles of self regulation theory(17-18). Self regulation has been described as a process that has three distinct stages; self monitoring, self evaluation and self reinforcement.  Self monitoring is a method of systematic self observation, periodic measurement and recording of target behaviours with the goal of increasing self awareness. The awareness fostered during self monitoring is considered an essential initial step in promoting and sustaining behaviour change. Strong evidence supports the role of self monitoring as an effective strategy in the health behaviour change process.  Reviews by Michie et al of effective behavioural techniques for healthy eating, physical activity and reduction of alcohol consumption concluded that self-monitoring was effective alone, but when combined with other techniques the effect size nearly doubled(19-20).  We have recently completed a systematic review of RCTs to examine the effectiveness of self weighing as a strategy for weight loss(21). One study examined self weighing as a single strategy and it was ineffective (-0.5 kg 95% CI -1.3 to 0.3) but adding self-weighing/self-regulation techniques to programmes resulted in a significant difference of -1.7 kg (95% CI -2.6 to -0.8). Multi-component interventions including self-weighing compared to no/minimal control also resulted in mean differences of -3.7 kg (95% CI -4.6 to -2.9).