Cancer is a disease that disrupts the body’s genetic composition, causing instability in the genome. Moreover, despite notable progress in cancer treatment, the enduring global impact of cancer-related fatalities persists. Recognizing the substantial impact of diet on overall health, interventions such as caloric restriction and fasting are being explored for their potential benefits in disease prevention and promoting longevity. The well-established epidemiological correlations between obesity and cancer further underscore the critical role that adopting healthy dietary practices can play in reducing the risk of cancer, specifically, the intricacies of how diet influences cancer progression and its implications for treatment outcomes represent a less-explored realm in current research. In this chapter, we aim to unravel the complex interplay between dietary choices and their potential impact on various aspects of cancer, with a particular focus on understanding how diet can shape and influence the effectiveness of cancer prevention or treatments. Moreover, our examination extends to elucidating potential pathways by which diet might positively influence cancer outcomes, encompassing hormonal regulation, metabolic processes, and immune and inflammatory responses. The available literature on this subject is relatively sparse, highlighting the need for more comprehensive research efforts. Although data remain limited, preliminary findings suggest that dietary interventions have the potential to mitigate treatment-related toxicity, enhance the efficacy of chemotherapy, and reduce the risk of enduring complications in cancer patients. Thus, it is paramount to deepen our understanding and advance the scientific exploration of this significant yet intricate adjunctive strategy in cancer treatment. The substantial and expanding body of evidence supporting the incorporation of various factors into lifestyle modifications has the potential to enhance the formulation of lifestyle guidelines in various contexts, as elaborated upon in the forthcoming chapter.