This report is the first to present process data regarding the coach-participant interaction during the successful DPP lifestyle intervention. A main finding of this clinical trial was that a goal-based behavior change intervention was more efficacious than drug or placebo treatment in delaying diabetes onset over 3.2 years [1, 2]. Although an ethnically and racially diverse group of lifestyle participants succeeded, on average, the current analysis showed that they had to manage a wide variety of problems to do so. For dissemination it is helpful to examine the major barriers and the different types of lifestyle coaching approaches used to improve short and long term adherence. First, the diet and activity barriers and their demographic variability are characterized followed by a discussion of the most common lifestyle coaching approaches used.
This analysis showed that self-defeating thoughts and mood, problem social cues, and disrupted physical activity routines were more common for women than men, younger compared to older persons for some barriers, and working compared to retired persons for others. These findings extend previous data showing that DPP lifestyle participants over the age of 60 had better session attendance, turned in more food records and demonstrated more favorable long term weight loss, physical activity participation,  diabetes delay and other biometric outcomes . One implication is that in DPP translation, barriers (or the perception of barriers) do appear related to longer term adherence and outcomes and should be addressed proactively. Another implication is that individuals over aged 60 represent a particularly “ready” subgroup for translational programs because their barriers (or perceptions of barriers) are fewer. Future studies should evaluate the cost-effectiveness of delivering lifestyle interventions to older adults whose disease risks and costs are otherwise expected to accelerate sharply.
Another implication for future research is that younger and middle-aged individuals, particularly women, appear to need amplified social support, to address common barriers including access to interventions that fit more seamlessly into the context of their daily routines. Research by Wing and Jeffery  and others  has demonstrated the benefits of recruiting participants with friends to increase social support for weight maintenance. Targeting naturally occurring social groups such as friends, co-workers, or those with common life circumstances (e.g. high risk mothers with preschoolers) may be a fruitful avenue for diabetes prevention translation. Face to face interaction has consistently been shown to be most effective for weight loss and maintenance [52, 53], however telephonic and web-based approaches are increasingly being utilized as a cost-effective means to extend the reach and scope of intervention support [16, 24, 25, 52, 53].
In addition, the data suggest that a significantly larger proportion of non-Caucasians compared to Caucasians (roughly 10-20% more) were found to have multiple barriers, independent of socioeconomic status. Lower household income and less education was significantly associated with less frequent dietary self-monitoring. Self-monitoring of physical activity did not appear to be a problem for most DPP participants, but access to places to exercise or weather-related challenges were more commonly reported for racial and ethnic minorities compared to Caucasians. Because dietary self-monitoring and feedback is highly correlated with weight loss success [3, 37, 57], we conclude that a more accessible array of dietary self-monitoring tools is needed. Mobile applications (e.g. smart phones), especially those that offer real-time feedback, have been shown to enhance self-monitoring adherence  but this may not be accessible for some population subgroups. Prior research has examined flexible, alternate forms of dietary self-monitoring for those who do not adhere to traditional methods (e.g. picture-based checklists of commonly eaten foods and portion sizes)  but more studies are needed.
A second major finding of the current investigation is that problem-solving was the dominant short and long term coaching approach for the full range of barriers with the majority of participants. This type of approach was used with most but not all participants during the first 16 sessions of lifestyle intervention; subsequently it essentially became the basis for the coach-participant interaction. As barriers increased over the course of treatment, lifestyle coaches also turned to some more costly methods (e.g., those with low translation potential). The implication for dissemination research is that effective curriculum delivery must go well beyond didactic teaching in helping participants develop more autonomy for anticipating and responding to personal barriers and lapses. Previous obesity intervention research does not provide a unified prescription on how best to achieve this but several studies have emphasized the importance of addressing the self-defeating thoughts often associated with behavioral avoidance and relapse [40, 60–64]. The IMAGE toolkit approach in Europe has also strongly emphasized the consistent use of behavior change processes that include self-monitoring and feedback, problem solving for relapse prevention, and seeking community-based social support [32, 33]. We conclude that future intervention design and training of lifestyle coaches would do well to increase time spent on the practice and facilitation of problem-solving approaches. Review of dietary self-monitoring skills was the second most common coaching approach used during the short and long term intervention. Another translational consideration, therefore, is that one-on-one diary review and feedback is very time consuming for lifestyle coaches. Novel use of trained lay health coaches (e.g. alone or in conjunction with a dietician) or peer group interaction to facilitate self-monitoring review and feedback, or other digital-interactive methods may accomplish similar ends and deserve further study.
Contrary to what has been assumed regarding the DPP intervention , monetary based approaches (e.g. rewards for behavior change, gym memberships) were utilized for fewer than 10% of DPP participants during the first 16 sessions. Research findings have been mixed on the utility of such incentives in promoting health behavior change ; our results indicate they were not central to the success of the intervention. However, added-cost toolbox approaches did increase to up to 75% of participants (e.g., staff-time due to increased number of phone calls or sessions) as barriers became more evident. It is clear that many participants will benefit from ongoing behavioral counseling assistance beyond the initial six months of intervention. How best to address this need for continued primary prevention contact in the current health care environment is a critical empirical and policy question.
There are several limitations to these analyses. One is that the data was exclusively reported by the lifestyle coaches and no corollary measures were obtained from the participants, thus there is risk of a systematic reporting bias. Documentation of the treatment approaches (toolbox strategies) used was more objective because the actual methods were targeted in session and reported immediately afterwards. Another limitation is that data on the participants’ baseline or post-intervention problem-solving skills was not collected; such measures should be incorporated into future translational studies.