Why are we doing this study? 

For patients living with kidney failure on haemodialysis, a transplant is considered the optimal treatment. However, patients also living with obesity experience substantially reduced access to transplant assessment due to weight-related concerns. There is a lack of high-quality evidence to inform clinical practice for this patient demographic and as a result, care can vary substantially between kidney centres, and sometimes even within the same centre. This absence of robust data has created inequitable and inconsistent care pathways for this patient population. 

INFILTRATE is a randomised feasibility study to assess whether a low‑energy diet programme can be delivered safely and acceptably to patients living with obesity and kidney failure on haemodialysis to support weight loss and improve access to the kidney transplant waiting list. Demonstrating feasibility will provide a foundation for a larger multi-centre study to assess effectiveness to inform future clinical practice, which will hopefully reduce variation in care, support patients and improve equitable access to transplant assessment and listing. 

Why does this matter for people with kidney failure? 

Despite national guidance indicating that obesity alone should not prevent kidney transplant assessment and eligibility, many patients are not activated on the transplant list due to weight-related concerns. Consequently, a proportion of patients are denied the opportunity to be considered for this potentially life-saving treatment and must remain on haemodialysis, which impacts directly on the patients by reducing their quality of life, mental health and increasing risk of complications. 

How could weight loss support kidney transplant access? 

For some individuals living with both kidney failure and obesity, a reduction in their weight may improve their chances of being considered for transplant listing. However, achieving and maintaining weight loss in this population is particularly challenging. Patients are often having to manage the substantial physical and mental effects of dialysis, dietary and fluid restrictions, fatigue, multiple comorbidities, and the psychological impact associated with kidney failure. 

As a result, this study extends beyond just a dietary intervention and incorporates tailored physical activity and mental health support to address the broader factors impacting on people being able to achieve long-term weight loss. The study aims to generate evidence on feasible, patient‑centred strategies that may support equitable access to transplant assessment. The intervention was co-designed with patients currently living with obesity and kidney failure through interviews and workshops. 

What will happen during the study? 

Eligible participants will be randomly allocated to one of two study arms: an intervention group or a usual‑care control group. Participants assigned to the intervention arm will receive the lifestyle programme described below, while those in the control arm will continue with standard clinical care as currently delivered. 

All participants will be reviewed at three‑monthly intervals over a 12‑month follow‑up period. Study visits will include health checks, body measurements, questionnaires, and planned conversations with members of the research team. All study visits will take place within participants’ usual dialysis units on their routine dialysis days, preventing loss to follow up while decreasing the impact on the patient.  

Intervention components 

The intervention comprises three combined components—DIET, MOVE, and MIND—designed to address dietary, physical, and psychological dimensions of weight management in people with living with kidney failure and obesity. 

DIET: Total diet replacement 

Participants in the intervention arm will have a 12‑week period of total diet replacement. During this phase, participants will consume nutritionally complete meal‑replacement products provided by Counterweight Ltd.  

Recognising the importance of fluid management in CKD, the volume of fluid used to prepare products will be individually tailored to align with each participant’s prescribed fluid restrictions. Participants will receive regular support and monitoring from the Counterweight dietetic team throughout this phase to ensure safety and provide clinical oversight. 

MOVE: Physical activity support 

Following completion of the diet replacement phase, participants will commence the MOVE component of the programme which is delivered over a subsequent 12‑week period. This consists of a kidney‑specific digitally delivered exercise programme by Kidney Beam, designed to be appropriate and accessible for individuals living with CKD. 

The programme aims to improve physical function, build confidence in physical activity, and support overall health and wellbeing. At the conclusion of this phase, participants will receive individualised physical activity recommendations to support them in the longer‑term. 

MIND: Psychological support 

The intervention also incorporates a psychological component (MIND) addressing the behavioural and emotional aspects of weight management. This includes structured sessions delivered by members of the research team, focusing on topics such as eating behaviours and emotional eating, or topics that are brought up by the group. 

Participants requiring additional psychological support will be assessed and signposted or referred to appropriate local services in line with existing care pathways. Monthly peer‑support groups will also be offered, facilitated by the research team but shaped and led by participants. These groups are intended to provide mutual support and shared learning, acknowledging the complex emotional and psychological challenges associated with weight, food, and CKD.  

How was this kidney study programme developed? 

The programme was developed by Dr Adrian Brown and is informed by existing evidence from low‑energy diet interventions that have demonstrated effectiveness across several other patient groups. Previous studies have reported clinically meaningful weight loss and associated improvements in metabolic outcomes. For example, a trial involving individuals with advanced type 2 diabetes treated with insulin reported a mean weight reduction of approximately 10 kg at 12 months, with 40% of participants able to discontinue insulin therapy. In addition, a study conducted in patients living with CKD found that 46% of participants achieved a weight loss of at least 10 kg at 12 months. 

This evidence, coupled with expertise from prior kidney‑specific research, informed the design of the current study. Dr Helen McLaughlin, a contributor to the CKD study, is a member of the trial management group and provides clinical and methodological support to ensure the feasibility of this study within this patient population. 

Who is leading the study? 

The study is led by Dr Adrian Brown, a senior specialist dietitian, NIHR Advanced Fellow and Associate Professor at the Centre for Obesity Research, UCL. He is the Chief Investigator for INFILTRATE. 

The wider team brings together experts in kidney care, transplant surgery, obesity, psychology, physiotherapy, exercise, and research delivery. 

Study team 

• Claudia Hobbs ANutr– Research Assistant  

• Professor Reza Motallebzadeh – Honorary Consultant Renal Transplant Surgeon, Royal Free Hospital  

• Dr Kieran McCafferty – Consultant Nephrologist, Royal London Hospital  

• Professor Rachel Batterham – Honorary Professor of Obesity, Diabetes and Endocrinology, Centre for Obesity Research, UCL  

• Dr Sebastian Potthoff – Chartered Health Psychologist and Associate Professor of Behavioural and Implementation Science, Northumbria University  

• Dr Helen McLaughlin – Associate Professor and Advanced Clinical Researcher, Queensland University of Technology  

• Dr Sarah Afuwape – Consultant Health Psychologist and Honorary Associate Professor, Royal Free Hospital  

• Professor Sharlene Greenwood – Consultant Physiotherapist and Professor of Exercise and Lifestyle Therapy, King’s College Hospital  

• Anna Bell-Higgs – Partnerships Manager, Counterweight Ltd  

What do we hope will happen after the study? 

This study aims to evaluate the feasibility, safety, and acceptability of the programme for patients living with obesity and CKD. Demonstration of feasibility would support progression to a full‑scale randomised controlled trial. In the longer term, the findings are intended to inform clinical practice and contribute to the development of more equitable and consistent access to kidney transplantation for this patient group. 

If you would like to get in touch, please email claudia.hobbs@ucl.ac.uk 

Link to the ISRCTN Study Registry