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The rising challenge of severe obesity

Overweight and obesity now affect two thirds of adults (over 30 million people) in the UK. This significantly increases risks of death from heart disease and cancer, and jeopardises prospects for further improvements in life expectancy. Moreover, severe obesity (often defined as Body Mass Index > 40 kg/m2, or BMI > 35 kg/m2 if accompanied by comorbidity) is also increasingly common. About 7-9% of adults have BMI>35, and 3-5% of middle aged adults have BMI>40 kg/m2. There are also significant gender and ethnic variations. Once relatively rare, severe obesity affects millions of people and has become a common reason for medical referral.

However, severe obesity poses considerable challenges to individuals and the NHS. The principal challenge for health services is that with the specific exception of bariatric surgery, the optimum long term management of severe obesity, and its effectiveness are poorly defined.


Current weight management services

In the UK, resources for prevention and treatment of overweight and obesity are categorised into four “tiers”. Tier 1 represents non-medical community based resources; Tier 2 are primary care based resources and treatment programme; Tier 3 services are specialist multidisciplinary services designed for assessment and treatment of patients with severe obesity that has not responded to earlier interventions; Tier 4 services are bariatric surgical units.
Although NICE has advocated the principles of multidisciplinary, personalised behavioural intervention for Tier 3 clinics, the optimum design and delivery of such interventions is poorly researched.

Group-based behavioural intervention in Tier 3 services?

Tier 3 services face several major challenges. On the one hand there are rising numbers of referrals and limited resources, and on the other hand the evidence base for Tier 3 intervention is lacking. Therefore, rational commissioning decisions are problematic, as commissioners and providers do not know how best to structure and deliver interventions. Moreover, rising demand makes one-to-one delivery of behavioural intervention increasingly unrealistic. While one alternative may be group based behavioural intervention, it is not understood how these different aims can be reconciled.
There is already fairly widespread use of group activities in Tier 3 services, but this is primarily for information giving and educational purposes. On the other hand, use of group-based behavioural intervention as the core intervention in the Tier 3 service is unusual. The optimum design, delivery and effectiveness of group-based behavioural intervention programmes in Tier 3 is poorly understood.

Project aims and objectives

This research programme was established to investigate the evidence base for Tier 3 interventions, and specifically to test the idea that a group-based behavioural intervention can be an effective model of care for these services.

Project activity

Working with a national team of specialist service providers, service users, Tier 3 commissioners, dietician, psychological and implementation science experts we have devised a proposal to optimise how the dynamics of how a group-based service for people with severe obesity may be developed and used.

Plymouth-based project staff

Other Site Co-applicants


Related publications

Watkins R, Swancutt D, Alexander M, Moghadam S, Perry S, Dean S, Sheaff R, Pinkney J, Tarrant M & Lloyd J (2023) 'A Qualitative Exploration of Patient and Staff Experiences of the Receipt and Delivery of Specialist Weight Management Services in the UK' The Patient - Patient-Centered Outcomes Research, DOI, Open access.
Swancutt D, Tarrant M, Ingram W, Baldrey S, Burns L, Byng R, Calitri R, Creanor S, Dean S & Evans L (2022) 'A group-based behavioural intervention for weight management (PROGROUP) versus usual care in adults with severe obesity: a feasibility randomised controlled trial protocol' Pilot and Feasibility Studies 8, (1).
Tarrant M, Khan SS, Farrow CV, Shah P, Daly M, Kos K (2017). Patient experiences of a bariatric group programme for managing obesity: A qualitative interview study. British Journal of Health Psychology,22, 77-93.
Steele, T , Narayanan, RP , James, M , James, J , Mazey, N and Wilding, JPH (2017). Evaluation of Aintree LOSS, a community-based, multidisciplinary weight management service: outcomes and predictors of engagement. Clinical Obesity, 7 (6). 368 - 376.
Borek, A. J., Abraham, C., Greaves, C. J. and Tarrant, M. (2018), Group-Based Diet and Physical Activity Weight-Loss Interventions: A Systematic Review and Meta-Analysis of Randomised Controlled Trials. Appl Psychol Health Well-Being.
Farrow CV, Tarrant M, Khan SS (2017). Using social identity to promote health: The impact of group memberships on health in the context of obesity. In: Buckingham S, Frings D, Albery IP, eds. Addiction, Behavioural Change and Social Identity: Routledge.