Cancer metabolism has long been associated with aerobic glycolysis, but recent research shows that cancer cells actively reprogram their metabolism to support anabolic growth, not as a passive response to mitochondrial damage. This reprogramming is driven by oncogenes and tumor suppressors, and metabolites themselves can be oncogenic by altering signaling and blocking differentiation. Altered metabolism is now recognized as a core hallmark of cancer, not just a secondary effect of proliferation. Warburg's original hypothesis that cancer cells use aerobic glycolysis due to mitochondrial defects is outdated. Most tumor mitochondria are functional, and metabolic reprogramming is essential for macromolecular synthesis. Recent studies show that cancer cells use mitochondrial enzymes for biosynthesis, not just for ATP production. The PI3K/Akt/mTORC1 pathway drives anabolic metabolism by reprogramming mitochondria. HIF-1, another key player, inhibits mitochondrial metabolism, which can be anti-proliferative. Myc also impacts mitochondrial metabolism by promoting glutamine utilization. Metabolic enzymes like PKM2 are alternatively spliced to support anabolic growth. PKM2's lower activity allows for the accumulation of glycolytic intermediates, which are shunted into anabolic pathways. PKM2 also has non-metabolic functions, such as nuclear translocation. Mutations in metabolic enzymes like IDH1 and IDH2 produce 2-hydroxyglutarate (2HG), an oncometabolite that disrupts epigenetic regulation and cellular differentiation. 2HG is a biomarker for IDH mutations and is linked to tumorigenesis. Other oncometabolites, such as succinate and fumarate, also play roles in cancer by modulating epigenetic processes. Cancer cells prioritize carbon flux into anabolic pathways over maximizing ATP production. This is supported by alternative glycolytic pathways and reductive carboxylation. The study of cancer metabolism has shifted focus from ATP production to metabolic reprogramming. Despite advances, challenges remain in distinguishing mitochondrial and cytosolic metabolites and quantifying metabolic flux. Overall, cancer metabolism is a complex, actively reprogrammed process driven by oncogenes and tumor suppressors, with altered metabolism now recognized as a core hallmark of cancer.Cancer metabolism has long been associated with aerobic glycolysis, but recent research shows that cancer cells actively reprogram their metabolism to support anabolic growth, not as a passive response to mitochondrial damage. This reprogramming is driven by oncogenes and tumor suppressors, and metabolites themselves can be oncogenic by altering signaling and blocking differentiation. Altered metabolism is now recognized as a core hallmark of cancer, not just a secondary effect of proliferation. Warburg's original hypothesis that cancer cells use aerobic glycolysis due to mitochondrial defects is outdated. Most tumor mitochondria are functional, and metabolic reprogramming is essential for macromolecular synthesis. Recent studies show that cancer cells use mitochondrial enzymes for biosynthesis, not just for ATP production. The PI3K/Akt/mTORC1 pathway drives anabolic metabolism by reprogramming mitochondria. HIF-1, another key player, inhibits mitochondrial metabolism, which can be anti-proliferative. Myc also impacts mitochondrial metabolism by promoting glutamine utilization. Metabolic enzymes like PKM2 are alternatively spliced to support anabolic growth. PKM2's lower activity allows for the accumulation of glycolytic intermediates, which are shunted into anabolic pathways. PKM2 also has non-metabolic functions, such as nuclear translocation. Mutations in metabolic enzymes like IDH1 and IDH2 produce 2-hydroxyglutarate (2HG), an oncometabolite that disrupts epigenetic regulation and cellular differentiation. 2HG is a biomarker for IDH mutations and is linked to tumorigenesis. Other oncometabolites, such as succinate and fumarate, also play roles in cancer by modulating epigenetic processes. Cancer cells prioritize carbon flux into anabolic pathways over maximizing ATP production. This is supported by alternative glycolytic pathways and reductive carboxylation. The study of cancer metabolism has shifted focus from ATP production to metabolic reprogramming. Despite advances, challenges remain in distinguishing mitochondrial and cytosolic metabolites and quantifying metabolic flux. Overall, cancer metabolism is a complex, actively reprogrammed process driven by oncogenes and tumor suppressors, with altered metabolism now recognized as a core hallmark of cancer.