**Background:** Prior randomized controlled trials have demonstrated that lifestyle changes promoting 5–7% weight loss and moderate physical activity can prevent or delay type 2 diabetes in individuals with prediabetes. However, the impact of lifestyle interventions on self-regulatory factors such as self-efficacy, goal commitment, and hopeful thinking has not been widely reported beyond the original Diabetes Prevention Program (DPP). Little research has examined whether participants can improve self-regulatory skills and achieve behavioral change if treatment is altered to better meet the needs of early slow responders. This study implemented and evaluated a 4-month adaptive lifestyle intervention for early slow responders during a diabetes prevention trial at a university worksite, grounded in an integrated conceptual framework combining Goal Setting Theory and Hope Theory.
**Methods:** Study participants were university employees ≥21 years old with prediabetes and overweight or obesity. The study employed a stratified research design in which two interventions were delivered through weekly, group-based sessions. Percent weight change was determined following the first 4 sessions; failure to achieve >2.5% weight loss at the beginning of session 5 was defined as slow early response, and these participants were stratified to the adaptive intervention (GLB+). Participants who achieved >2.5% weight loss remained in the standard intervention (GLB). The GLB intervention was a group-based version of the DPP intervention with goals of losing ≥7% of baseline weight, achieving ≥150 min/week of moderate PA, and reducing dietary fat intake to <25% of energy intake. The GLB+ intervention included discussion of individual health-related values, setting SMART goals, identifying pathways to achieve goals, developing strategies for overcoming obstacles, and creating goal maps. Outcomes included self-efficacy for weight control (Weight Efficacy Lifestyle Questionnaire), self-efficacy for eating and physical activity, self-regulation for physical activity, goal commitment, goal difficulty, goal satisfaction, state hope (agency and pathways), social problem-solving, dietary intake (Block FFQ), and physical activity (Fitbit Flex 2 accelerometer). Between-group differences were assessed using repeated measures analysis of variance with a Bonferroni-corrected significance threshold of P<0.0125.
**Key Results:** Two hundred thirty-two people initiated the intervention, 208 were stratified at week 5, and 185 completed outcomes at 4-months. There were no significant differences between groups at baseline except for sex (GLB+ had more females, P=0.0026). At 4-months, there was a significant difference between groups in the change in "sticking to healthy eating" (GLB: +2.32±0.41 vs GLB+: +0.47±0.36, P=0.0008) and "sticking to physical activity" (GLB: +3.88±0.87 vs GLB+: -0.38±0.75, P=0.0003) subscales. GLB participants also reported greater satisfaction with weight loss compared to GLB+ (P<0.0001). Both groups showed significant improvements in Weight Efficacy Lifestyle Questionnaire total scores (GLB: +16.52±3.19, P<0.001; GLB+: +12.07±2.79, P<0.001), physical activity self-regulation (GLB: +11.65±1.15, P<0.001; GLB+: +8.71±1.00, P<0.001), and goal commitment (GLB: +1.81±0.42, P<0.001; GLB+: +1.25±0.37, P<0.001). Only GLB+ participants reported a significant increase in pathways thinking (+0.97±0.26, P<0.01). Both groups significantly reduced energy intake (GLB: -429±58 kcal, P<0.0001; GLB+: -313±50 kcal, P<0.0001) and total fat intake (GLB: -23.15±2.87 g, P<0.001; GLB+: -16.95±2.48 g, P<0.001). GLB participants showed a significantly greater increase in very active minutes of PA compared to GLB+ (GLB: +63.27±13.18, P<0.0001; GLB+: +16.48±11.68, P=0.0087 for between-group difference). GLB attended significantly more sessions (14.09±0.18 vs 12.82±0.24, P=0.0003), but GLB+ reported more days of ≥10 continuous minutes of PA (52.25±2.78 vs 42.03±2.80, P=0.0091).
**Clinical Implications:** This study demonstrates that both standard and adaptive lifestyle interventions can improve self-regulatory outcomes, dietary intake, and physical activity in adults with prediabetes. The adaptive intervention (GLB+) successfully improved hope, goal commitment, and self-efficacy for resisting eating in high-risk situations while reducing calorie and fat intake among early slow responders. However, the significantly greater improvements in self-efficacy for sticking to healthy eating and physical activity in the GLB group suggest that GLB+ may need strengthening to improve participant confidence for persisting with diet and exercise behaviors. The finding that only GLB+ participants showed significant increases in pathways thinking supports the value of goal mapping and problem-solving activities. The significant correlations between self-regulatory outcomes and behavior change (e.g., PA self-regulation strategies correlated with very active PA minutes in GLB+, r=0.34, P<0.01) reinforce the importance of targeting self-regulatory processes in diabetes prevention programs. Future research should examine mediators of change and whether they differ for early slow responders versus early successful responders to enable greater tailoring of interventions.