| 1. Aim to promote changes in both diet and physical activity | Yes/no (1,0) |
| 2. Use established, well-defined behaviour change techniques (e.g. specific goal-setting, relapse prevention, self-monitoring, motivational interviewing, prompting self-talk, prompting practice, individual tailoring, time management) | Yes/no (1,0). Yes is scored if, as well as basic information provision, it includes ≥ 3 techniques from table 14 in the IMAGE guideline (which provides definitions used by NICE and other reviewers), or from a recognised taxonomy of behaviour change techniques (Michie et al.236) |
| 3. Work with participants to engage social support for the planned behaviour change (i.e. engage important others such as family, friends and colleagues) | Yes/no (1,0). Yes is scored if participants are encouraged to identify and seek social support outside the group (i.e. in their day-to-day lives). Encouraging social support within the group in a group-based intervention is not sufficient to code yes |
| 4. Maximise the frequency or number of contacts with participants (within the resources available) | High/medium/low (2,1,0), based on median split of total number of contacts
Structured physical activity (e.g. gym-based exercise) sessions that were offered have not been counted, as they are assumed not to involve a substantial interactive component. Written contacts (newsletters, etc.) were not counted |
| 5. Use a coherent set of ‘self-regulatory’ intervention techniques (specific goal-setting, ideally with coping planning, also known as ‘relapse prevention’); prompting self-monitoring; providing feedback on performance; problem-solving; review of behavioural goals) | Yes/no (1,0). Yes is scored if the intervention includes goal setting, self-monitoring (of outcomes or behaviours) and at least one other self-regulation technique [providing feedback on performance, problem-solving (relapse prevention), revising action plans in the light of performance] |
| 6. Use a group size of 10–15. This recommendation is designed to balance cost and effectiveness, rather than to be an exact specified range, so we coded for ‘a group size of no more than 15’ (the point at which effectiveness is expected to be diminished) | Yes/no (1,0). If a range was reported for group size (e.g. groups of 15–20), the mid-point of the range was used for coding purposes
If individual (one-to-one) intervention was used, then a yes is coded (1 case) |
| 7. Provide at least 16 hours of contact time over the first 18 months | Yes/no (1,0). Contact time is assumed to be 1 hour per group session if session length is not stated (one case) or 10 minutes for a telephone contact (two cases), 30 minutes for an individual counselling session (one case) and 15 minutes for a GP visit (one case) |
| 8. Ensure programmes adopt a person-centred, empathy-building approach | Yes/no (1,0). Coded as yes if it is explicitly stated that a person-centred, empathy-building or empowerment theory-based approach was used throughout, or if motivational interviewing or other empathy-building techniques are specified |
| 9. Allow time between sessions, spreading them over a period of 9–18 months | Yes/no (1,0) |
| 10. Information provision: to raise awareness of the benefits of and types of lifestyle changes needed | Yes/no (1,0) |
| 11. Exploration and reinforcement of participants’ reasons for wanting to change and their confidence about making changes | Yes/no (1,0) |
| 12. Gradual building of confidence (self-efficacy) by starting with achievable and sustainable short-term goals and setting of graded tasks | Yes/no (1,0) |
| 13. Use a logical sequence of intervention methods (e.g. motivation, action-planning, maintenance) | Yes/no (1,0) |
| Total IMAGE guidance score | Possible maximum score of 6 points:
1 point for each yes for items 1, 2, 3 and 5. For item 4, score 2 points for a high amount of contact, 1 point for a medium amount |
| Total NICE guidance score | Possible maximum score of 12 points:
IMAGE score (as above but without item 4, which overlaps with item 7) plus 1 point for each yes for items 6–13 |
| 14. Intervention fidelity checking | We also coded whether or not the developers used specific methods to check intervention fidelity (e.g. monitoring the first four sessions and giving formative feedback) |
