Background: Self-rated adherence and qualitative feedback may be useful in monitoring and understanding participants’ compliance during lifestyle interventions. We examined self-rated adherence and qualitative feedback in the Healthy Diet and Lifestyle Study (HDLS). HDLS is a randomized pilot intervention comparing the effect of intermittent energy restriction combined with a Mediterranean diet (IER+MED) to a euenergetic Dietary Approaches to Stop Hypertension (DASH) diet, with matching physical activity regimens, for reducing visceral adipose tissue area (VAT) and weight.Methods: We analyzed the 59 (98%) participants who completed at least one week of HDLS. Self-rated adherence scores to dietary and physical activity prescriptions were collected 8 times across the 12-week intervention, using a 0-10 scale (0=Not at all, 4=Somewhat, and 10=Following the plan very well). Adherence scores for each participant were averaged and assigned to high and low adherence categories using the group median (7.3 for diet, 7.1 for physical activity). Mean changes in VAT and weight from baseline to 12 weeks are reported by adherence level, overall and by randomization arm. Participants qualitative feedback at completion of HDLS and 6 months post intervention were examined.Results: Overall, compared to participants with low self-rated adherence to dietary prescriptions, those with high adherence lost significantly more VAT (22.9 ± 3.7 cm2 vs. 11.7 ± 3.9 cm2; p=0.044) and weight at Week 12 (5.4 ± 0.8 kg vs. 3.5 ± 0.6 kg; p=0.045). For physical activity, compared to participants with low adherence, those with high adherence lost significantly more VAT (22.3 ± 3.7 cm2 vs. 11.6 ± 3.6 cm2; p=0.035). Participants’ qualitative feedback of HDLS was positive and the most common response, on how to improve the study, was to provide cooking education classes.Conclusions: Our results support the use of self-rated adherence to dietary and physical activity prescriptions as an effective method to monitor compliance and facilitate participant goal setting during a behavioral modification intervention. Study strategies were found to be effective with promoting compliance to dietary and physical activity prescriptions. The incorporation of cooking classes and demonstrations into future larger trials may further complement dietary adherence.Trial registration: ClinicalTrials.gov Identifier: NCT03639350. Registered 21st August 2018- Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03639350