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Obesity and behavioural changes

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


In the UK, clinical obesity is estimated to affect a quarter of the adult population, while nearly 2 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
  • depression

This creates a huge financial and clinical strain on NHS services. 

In 2016/17 there were over 600,000 hospital admissions where obesity was a factor, while Public Health England estimated the cost of obesity on the NHS in England at £6.1 billion 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.

Obesity and GP intervention

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 among 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. 

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 spent 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, they werebooked into the programme so that they left the surgery with an appointment. 

In the control group, the GP gave a 30-second intervention to encourage people to benefit their health by losing weight.

At 3 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 2 questions at the end of the consultation.

Obesity and the BWeL 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 was 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. 

Among the support group, uptake of the intervention offer was high, while the likelihood of a patient taking effective action to manage their weight was 5 times more common in the support group, than the advice group.

BWeL study 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 the 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 and teleconferences.

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.

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 to create an essential CPD e-learning module for their primary care membership, ‘Behavioural change and cancer prevention’. The 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

Further information

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