<p>Tumors exhibit metabolic fuel requirements resembling those of embryonic and other highly proliferative tissues, a similarity that can be exploited to combat neoplasia. However, several challenges limit the efficacy of dietary modifications in cancer therapy. This review explores how cancer cells acquire and catabolize macromolecules to harness energy and assesses the feasibility of influencing these pathways through dietary changes. Although dietary interventions modulate the energetic substrate supply to tumors only to a limited extent, they offer significant ancillary benefits by imposing hormonal states that burden cancer metabolism, enhancing immune responses, and reducing inflammation. Integrating dietary considerations into the standard of care for cancer patients represents a promising adjunct to traditional treatments, despite their dampened impact on nutrient availability for tumor energy metabolism.</p>