Background <p>Poor diet quality has been associated with greater risk of people developing overweight and obesity, type 2 diabetes, cardiovascular disease, and osteoarthritis. For each of these conditions, weight management is recommended in respective guidelines. Current weight management interventions, such as the Healthy Weight for Life™ (HWFL) program that uses meal replacements, have not been assessed for impact on diet quality. Further, the role of a dietitian providing medical nutrition therapy (MNT) in conjunction with the HWFL program has not been evaluated. MNT is an evidence-based approach where dietary interventions are tailored to the individuals needs, medical history, lifestyle, and dietary preferences. Therefore, the primary aim of this pilot study is to evaluate the feasibility, acceptability and preliminary impact of adding personalised (MNT) consultations to the HWFL program on diet quality. Secondary outcomes include weight and osteoarthritis scores .</p> Methods <p>An 18-week randomised control trial was undertaken, with eligible HWFL program participants randomised to either usual care arm (HWFL program) or HWFL + MNT. A food frequency questionnaire was used to assess diet quality (% energy from nutrient-dense core food) and provide intervention participants with personalised feedback on food and nutrient adequacy of their dietary patterns. Weight and knee osteoarthritis outcomes using the hip and knee osteoarthritis outcome scores, were self-reported and used to assess outcomes. Project acceptability was assessed by process evaluation questionnaire. An intention-to-treat analysis was undertaken using generalised linear mixed models with post-estimations reported as mean (95% CI).</p> Results <p>Forty participants (75% female, 62 ± 10years, 78% osteoarthritis) enrolled in the study. Baseline diet quality was poor (34% energy from non-core foods). Post-intervention both intervention and usual care groups significantly improved their diet quality and reduced weight, but there were no significant differences between groups. Sub-scores for knee osteoarthritis function significantly improved in the intervention compared to the control group (mean between group difference 17.4, 95% CI 1.6, 33.1), though after correcting for multiple testing this was no longer significant. Overall intervention acceptability was high.</p> Conclusion <p>Both the intervention and usual care arms significantly improved diet quality. All intervention participants found MNT was highly acceptable. For those with knee osteoarthritis significant improvements in knee osteoarthritis function was reported in the intervention group. This should be further explored in future interventions.</p> Trial registration <p>Australian New Zealand Clinical Trials Registry (ACTRN12623001062617).</p>