Not exactly. My understanding of the Warburg effect is that cells rely upon glycolysis for their _additional_ energetic demands but still have functioning mitochondrial with the ability to oxidise fats; a lot of the pentose phosphate pathway is upregulated in tumors as they're busy making amino acids for protein biosynthesis. Of course, tumours do literally everything imaginable somewhere so take this with a glacier sized disclaimer. The main thing is that the reactions that are favoured tend to be either anaplerotic (contributing carbon towards the Krebs cycle) or straight up anabolic. https://www.thelancet.com/journals/ebiom/article/PIIS2352-39...