unlike healthy cells, which generate energy by metabolizing sugar in their mitochondria, cancer cells appeared to fuel themselves exclusively through glycolysis, a less-efficient means of creating energy through the fermentation of sugar in the cytoplasm. The theory is simple: If most aggressive cancers rely on the fermentation of sugar for growing and dividing, then take away the sugar and they should stop spreading. Meanwhile, normal body and brain cells should be able to handle the sugar starvation; they can switch to generating energy from fatty molecules called ketone bodies — the body's main source of energy on a fat-rich diet — an ability that some or most fast-growing and invasive cancers seem to lack.
Here is another side to it. Two new studies that say that sugary diets promote gut cancer in mice by other mechanisms too:
Dietary carbohydrate source alters gene expression profile of intestinal epithelium in mice.
High Sucrose Diets Promote Intestinal Epithelial Cell Proliferation and Tumorigenesis in APC(Min) Mice by Increasing Insulin and IGF-I Levels.