The goal of this study is to evaluate the effectiveness of a skills training group informed by polyvagal theory, when delivered in an NHS setting, for those living with obesity. Polyvagal Theory in Therapy encourages individuals to be curious, respect how their nervous system works, and notice and respond to bodily sensations. Research shows that interoception, which is the ability to sense and understand what is happening inside the body such as recognising hunger, pain, or emotions, may be challenging for people in larger bodies. These challenges have been connected to difficulties in managing emotions which may lead to behaviours such as emotional eating. This points to the need for a therapeutic approach that helps people both notice what's happening in their bodies and trust those signals enough to be able to respond in healthy ways. This project will test whether a novel polyvagal informed skills training group can improve body awareness (interoception) and emotional regulation for people within an NHS specialist weight management service using a single case experimental design. Participants will be randomly assigned a baseline period of either 14 or 21 (phase A of the design) using computer-generated randomisation. During this phase, participants will complete outcome measures. The skills training intervention phase (phase B) will begin immediately following the individual's baseline period. The intervention is the six session group polyvagal theory-informed skills training. A four-week follow-up period will follow the skills training group, during which participants will continue to complete the same outcome measures they had used in the first two phases. This phase will help assess whether immediate treatment gains are maintained and/or whether delayed treatment gains occur. Trend analysis within this phase will show whether improvement or decline occurs post-skills training.

This study will be a quantitative multiple baseline study using a within-subjects' single case experimental design. The study will take place over three phases; the baseline phase, the skills training intervention phase and the follow-up phase. For the baseline phase, participants will be randomly allocated a baseline period of either 14 or 21 days using an online random number generator, and the intervention (group skills training) will start immediately after the baseline period ends. The skills training phase is six sessions of polyvagal theory-informed skills training delivered in a group that will take place over nine weeks (three weekly sessions and three fortnightly). The intervention effect will be measured through three daily visual analogue scales and two weekly standardised measures. Outcomes will be compared at the same stages across participants. A four-week follow-up period will take place after the skills training. Participants will complete outcome measures throughout all phases. Participants will be asked to commit to a study lasting up to 16 weeks. The study will take place virtually, where questionnaires will be completed online and the group skills training will take place on an online video platform.

The participants will be patients from Ashford and St Peter's NHS Specialist Weight Management Service. They will be identified and approached by the clinical team during routine clinical contact and if the patient is interested in taking part, consent to share their details with the research team will be gained. Participants will be informed on the nature of the skills training group and provided with a video and information sheet explaining what the group will involve so they are able to decide if they wish to take part.

Participants will complete the University of Rhode Island Change Assessment (URICA) to identify their stage of change (Pre-contemplation, Contemplation, Action or Maintenance) before taking part and those in the pre-contemplation stage will not be included. Participants will be informed of this beforehand and it will be explained that this is to ensure that only those who will be best able to engage and make use of the group skills training attend the group and take part in the study, given the high level of commitment. Participants will also complete a demographics questionnaire asking them to self-report their gender, age category, ethnicity and state any comorbidities including physical health conditions, mental health conditions and neurodiversity. This information will not be used to identify the participants but will be used when considering collective group of participants and the generalisability of the findings.

In all phases, participants will complete a brief daily questionnaire in the form of a four question visual analog scale, asking participants to record the frequency they are noticing and responding to shifts in their body and engaging in an unwanted chosen behaviour, such as emotional eating. The fourth question will only be completed during the intervention and follow-up phase and asks participants to record the frequency of skills practice. Participants will also be asked to complete two short online questionnaires weekly that take up to 15 minutes to complete, the Difficulties in Emotion Regulation Scale and the Multidimensional Assessment of Interoceptive Awareness Version 2.

Participants will take part in a six-session group skills training with a Trainee Clinical Psychologist and qualified Clinical Psychologist under the supervision of the the research supervisor, a Clinical Psychologist and the treatment manual creator via video call, scheduled weekly for the first three sessions and fortnightly for the following three sessions, taking place over a nine-week period. Each session will be two hours long. The group will focus on understanding the autonomic nervous system, respecting changes in physiology as a result of the autonomic nervous system, and learning strategies to enhance body awareness and manage emotions, such as breathing exercises. The content of the sessions will include: introduction to polyvagal theory; application of polyvagal theory to client's difficulties; mapping on the polyvagal ladder; exercises to regulate up the ladder; practicing exercises and mapping on the ladder and summarising and skills training blueprint. Participants will be asked to practice techniques in sessions and applied independently between sessions with the chance to feedback on the application of ideas and techniques each session. Participants will be contacted via mobile phone or email to remind them of the group appointment and to complete daily and weekly questionnaires.

After participants have completed the group skills training, during the four-week follow-up phase, participants will complete a feedback form that will be used to assess the acceptability of the group. During this phase, participants will continue practicing learned techniques and continue to complete the daily and weekly questionnaires. At the end of the study, participants will be provided with a full debrief and signposted to further support if needed.

Inclusion Criteria:

• Able to commit to the duration of the study from baseline to end of follow up period (up to 16 weeks)
• Current service user of Specialist Weight Management Programme
• Aged 18-65.
• Good level of English spoken, reading and writing.
• Identified by the University of Rhode Island Change Assessment (URICA) to be in the Contemplation, Action or Maintenance stage of change.
• Access to device with internet connection to complete online questionnaires and with camera for online group sessions.

Exclusion Criteria:

• Identified by the University of Rhode Island Change Assessment (URICA) to be in Pre-contemplation stage of change
• Currently in psychological skills training treatment during the 16-week study period
• History of organic brain injury or cognitive impairment
• Clients presenting with suicidal intent