Interest in dietary and lifestyle interventions to prevent the progression of prostate cancer is driven by observational findings that dietary and lifestyle factors contribute towards prostate carcinogenesis and progression. However, the evidence-base to underpin the development of effective interventions is weak. This thesis describes investigations to inform future intervention studies for prostate cancer progression. Specifically the research focused on the association of adherence to dietary and lifestyle recommendations and prostate cancer risk in a nested case-control study of 1,806 PSA-detected prostate cancer cases and 12,005 controls in the Prostate for testing and cancer and Treatment (ProtecT) randomised trial; the relationship of dietary and lifestyle changes in a cohort of 621 ProtecT participants with localised cancer with post-diagnosis insulin-like growth factor-I (IGF-I) and IGF binding protein-3 (IGFBP-3) and the acceptability of a dietary and lifestyle interventions in African Caribbean prostate cancer survivors, including facilitators and barriers to dietary and lifestyle changes .. Greater adherence to the prostate cancer dietary recommendations and recommendations to increase plant foods and tomato products were inversely associated with prostate cancer risk. Next, healthy changes in protein, fruit and vegetable intake, body mass index (BMI), and physical activity following a prostate cancer diagnosis were associated with favourable changes in postdiagnosis serum IGF-I and IGFBP-3. Finally, the majority of the men interviewed did not make dietary and lifestyle changes following a prostate cancer diagnosis as they perceived their diet and lifestyle to be healthy and they were uncertain about the therapeutic benefits of these factors on disease recurrence. Intervention was deemed unnecessary since their PSA level was controlled by treatments and it was thought that dietary and lifestyle changes should stem from personal motivation. Nevertheless, concerns about their body weight and image were expressed and a desire to maintain good level of fitness. These findings suggests that future intervention studies for prostate cancer survivors might be plant-based including tomato products. Further evaluations of IGF-I and IGFBP-3 as surrogate markers for disease progression are needed. Additionally, an intervention may be more successful in African Caribbean men if it is targeted at those with high PSA levels and framed within an overall positive health message to prevent cancer recurrence and assist recovery from treatment.