...information for health professionals

Slimming World's research programme

Slimming World invests in the continued evaluation and development of our programme to ensure we continually improve our services to provide the best support for our members, to evaluate the effectiveness of our programme, and to ensure that our approach remains fully in line with national guidance.

Evidence of Slimming World's effectiveness

Highlights of some of Slimming World's extensive evidence-base are presented below. For a comprehensive summary of all Slimming World related evidence, you can download our full research portfolio here.


The largest published evaluation of a national lifestyle weight management service, comprising over 1.3 million U.K. Slimming World members, shows how participation in the weight loss program produced clinically significant weight losses at three months after joining the service.
Here’s a summary of the evidence.

N Mean joining BMI (kg/m2) Mean weight change (kg) Mean weight change (%) Mean BMI change (kg/m2) % Male
1,356,105 32.6 (6.3) -3.9 (3.6) -4.4% (3.8) -1.4 (1.3) 5.0%

Note: data presented are mean (SD)

Greater engagement with the service enhanced weight loss outcomes. For over 478,000 participants attending at least 75% of weekly sessions, weight loss was even more clinically significant.

N Mean joining BMI (kg/m2) Mean weight change (kg) Mean weight change (%) Mean BMI change (kg/m2)
478,772 33.2 (6.3) -6.8 (3.7) -7.5% (3.5) -2.5 (1.3)

Note: data presented are mean (SD)

Stubbs et al, 2015. Weight outcomes audit in 1.3 million adults during their first 3 months’ attendance in a commercial weight management programme. BMC Public Health 2015, 15:882.

The same dataset showed that weight outcomes continued to improve with long-term engagement. In a further evaluation of over 70,000 members attending at least 75% of weekly sessions over a 12-month period, participants lost more than 13% of their weight, which is highly associated with significant health benefits such as lowering the risk of developing type 2 diabetes, reducing high blood pressure and improving blood cholesterol.

N Mean weight change (kg) Mean weight change (%) Mean BMI change (kg/m2) Mean weeks attended % Male
71,989* -12.7 (8.4) -13.2% (7.4) -4.7 (3.0) 45.4 (86% of possible sessions) 6.3%

Note: data presented are mean (SD)

Lavin, J.H., Pallister, C., Morris, L. and Stubbs, R.J. (2013). 12 month weight outcomes in 45,395 high-engagers with the Slimming World weight management programme. Obesity Facts, 6(1):189.
*Data updated since publication

Slimming World on Referral efficacy

Slimming World on Referral is a subsidised partnership enabling health practitioners to refer patients to a local Slimming World group for weekly weight management support at no cost to the patient. Slimming World pioneered this NHS partnership programme with Greater and Central Derby Primary Care Trusts in 2001 and it is now an established obesity therapy in many Local Authorities, CCGs and workplaces. Evaluation shows the majority of patients referred by their health care team achieve clinically significant weight loss at three and six months.

N Referral length Start weight (kg) Mean weight change (kg) Mean weight change (%) % Male
34,271* 12 weeks 99.4 (20.0) -4.0 (3.7) -4.0% (3.6) 10.7%
4,7542** 24 weeks 108.2 (20.7) -8.9 (6.0) -8.6% (5.3) 12.1%

Note: data presented are mean (SD)

*Stubbs R.J, Pallister C, Whybrow S, Avery A, Lavin J. (2011) Weight Outcomes Audit for 34,271 Adults Referred to a Primary care/Commercial Weight Management Partnership Scheme. Obesity Facts 4:113-120
**Stubbs, R. J., Brogelli, D. J., Pallister, C. J., Whybrow, S., Avery, A. J. and Lavin, J. H. (2012), Attendance and weight outcomes in 4754 adults referred over 6 months to a primary care/commercial weight management partnership scheme. Clinical Obesity, 2: 6-14.

Facilitating healthy behaviour change

Slimming World’s lifestyle weight management program facilitates widespread behaviour change to support weight control in those engaging with the service, while also having a positive influence on the wider family network. We also look to understand how the program affects measures beyond just weight. In 2009, we surveyed 2,821 people to show the effective impact on behaviour change and health and wellbeing:

  • 78% reported buying more fruit and vegetables
  • 74% ate less fatty foods
  • 61% ate fewer sugary foods
  • 58% ate fewer packaged meals and take out
  • 37% had more energy
  • 33% reported they now enjoy exercise
  • 31% saw improvements in shape and posture
  • 29% had become more mobile in daily life
  • 25% saw mood improvements
  • 25% felt calmer and less stressed
  • 22% were sleeping better
  • 80% reported improved health

Not only did health and physical activity levels of those accessing Slimming World improve, but also that of their partners and children. This analysis was conducted on a representative sample of 2,812 from over 20,000 respondents accessing Slimming World’s participant support services and resources.

C. Pallister, A. Avery, J. Stubbs, and J. Lavin. 2009. Influence of Slimming World's lifestyle programme on diet, activity behaviour and health of participants and their families. Journal of Human Nutrition and Dietetics. 24(4), pp351-358.

Collaborating with Slimming World

We have an active research programme with many current projects underway. We are also keen to embark on future projects and collaborations to further develop support for people aiming to lose weight. Please contact us to discuss possible collaborations or research proposals you may have.