Internet Explorer is no longer supported by Microsoft. To browse the NIHR site please use a modern, secure browser like Google Chrome, Mozilla Firefox, or Microsoft Edge.

BWeL impact case study

Obesity affects around a quarter of the UK adult population, increasing the risk of significant long term health consequences. The BWeL study set out to assess the effect of a brief, opportunistic behavioural change intervention by GPs on clinically obese patients.

Published: 15 July 2019

The BWeL study was supported by the NIHR Clinical Research Network and funded by the UK National Research Initiative. Find out about the range of support available for NIHR primary care research here.

BWeL - impact case study

Screening and brief intervention for obesity in primary care (BWeL):
A parallel, two arm randomised control trial

Study aim

In the UK, clinical obesity is estimated to affect a quarter of the adult population, while nearly two thirds are classified as either overweight or obese. 

Obesity greatly increases the risk of significant long-term health consequences including type 2 diabetes, cancer, cardiovascular disease, disability and depression - creating a huge financial and clinical strain on NHS services. 

In 2016/17 there were over six hundred thousand hospital admissions where obesity was a factor, while Public Health England estimate the cost of obesity on the NHS in England at £6.1billion a year.

Guidelines recommend that GPs and primary care practitioners routinely screen and offer advice to their patients to motivate weight loss through behavioural weight loss programmes. Yet despite the high prevalence of obesity - primary care patient surveys and recordings of consultations indicate that GPs do not routinely intervene. Reported barriers to primary care interventions include insufficient appointment time and fear of causing offence.

The Brief intervention on weight loss (BWeL) trial set out to assess the effect of delivering a brief, opportunistic behavioural-change intervention within primary care services on weight loss amongst clinically obese patients. It was the first clinical trial to look at the potential impact that different opportunistic GP interventions may have on reducing obesity in primary care. 

Study summary

With CRN support, the trial took place across 57 GP practices in the south of England, with 137 primary care physicians taking part. 

The study team attended participating sites and sought consent to weigh and measure the height of patients waiting to see a GP. A total of 1,882 who agreed to take part were screened and eligible to be included in the intended to treat analysis. 

Participants were required to be at least 18 years old; have a body mass index (BMI) of at least 25/m² for Asian participants or 30/m² for other ethnicities; with a raised body fat percentage.  

Participants were randomly allocated to receive one of two possible brief interventions delivered by a GP at the end of a routine consultation. Half (940) were allocated to a support intervention, where the GP spend 30 seconds explaining that the best way to lose weight was by attending a behavioural weight loss programme, that it was free and available on the NHS.  If the patient agreed, s/he was booked into the programme so that they left the surgery with an appointment in her or his hand.  In the control group, the GP gave a 30-second intervention to encourage people to benefit their health by losing weight

At three months, participants were phoned by the researchers to assess actions undertaken to manage their weight. The study team then weighed 1,419 (75%) of participants as part of the 12 month follow up.

The primary outcome assessed was weight change from baseline to 12 months. Secondary outcomes included the proportion of participants who had lost 5% and 10% of their baseline body weight at 12 months; mean change in self-reported weight from baseline to 12 months; and mean change in self-reported weight from baseline to 3 months. In addition, the researchers assessed patients’ reactions to the GP’s opportunistic intervention by filling in two questions at the end of the consultation.

Key features:

•    Chief investigator: Professor Paul Aveyard, University of Oxford
•    Randomised trial delivered through 57 GP practices across the South of England
•    137 primary care physicians involved
•    8,403 patients screened for obesity in total: 1,882 participants eligible of the 2,256 who agreed to take part
•    Funded by: UK National Prevention Research Initiative

CRN involvement:

With NIHR Clinical Research Network (CRN) support, the trial was able to recruit to time and target - surpassing its original target by recruiting 1,882 participants against an original target of 1,824.

The CRN also provided support to identify suitable GP sites to take part, support with training and setting up practices, service support costs (SSCs) and teleconferences.

Study outcomes

After 12 months, the mean weight change for participants receiving the support intervention was 2.43kg, compared with 1.04kg for those who only received advice from their primary care physician - giving an adjusted weight loss difference of 1.43kg.  

At 12 months, 238 (25%) of the 940 participants in the support group had lost at least 5% of their body weight and 117 (12%) had lost at least 10%. These proportions were roughly double those in the control group.

Feedback from patients overwhelmingly positive - with 1,530 (81%) of participants describing the intervention as both appropriate and helpful, while only 4 participants (<1%) reporting that they found the intervention inappropriate and unhelpful. 
Amongst the support group, uptake of the intervention offer was high, while the likelihood of a patient taking effective action to manage their weight was five times more common in the support group, than advice group.

Impact for the NHS

The behavioural change intervention used in BWeL not only proved to be clinically effective and short enough to be deliverable within GP appointments, but also extremely cost effective - with the weight loss programmes costing in the region of £50 per patient.

With obesity linked to significantly increased risk of many serious health conditions, routinely incorporating similar weight loss interventions within primary care holds the potential to yield considerable cost savings for the NHS, while helping to tackle multimorbidities linked to obesity.

The study’s findings led to the publication of a Public Health England document, ‘Adult weight management: short conversations with patients’ - containing practical advice and tools to support health and care professionals in making brief interventions in weight management for adults.

The positive outcomes from BWeL also led the Royal College of GPs (RCGP) to create an essential CPD e-learning module for their primary care membership, ‘Behavioral change and cancer prevention’. The RCGP training course is aimed at healthcare professionals interested in promoting behavioural change to their patients - incorporating case studies and learning from the BWeL trial.

“As GPs, we don’t have anything to fear.  We can make opportunistic interventions to support weight loss, we can do so within 30 seconds, our patients will feel good about it, and a good number of them will benefit their health as a result.  It’s much simpler than anyone could have imagined it would be.”

Paul Aveyard, Chief Investigator of the BWEL study



Latest case studies