As the prevalence of smoking continues to decline, dietary factors are rapidly becoming the leading preventable cause of disease. Diet and obesity are also leading to a shift in cancer prevalence with increases noted in breast, liver, pancreas, and uterine cancers. Once cancer is detected, obesity is also associated with poorer outcomes with therapy as well as higher morbidity and mortality. Key factors are associated with the link between obesity and cancer including chronic inflammation, change in sex hormones, alteration in insulin‐IGF‐1 axis, alteration in adipokines, as well as cancer stem cells that are derived from adipose tissue. Because of these associations, a great deal of effort is being placed in implementing lifestyle changes that mitigate obesity‐associated factors that contribute to development of cancer, reduce side effects of treatment, and improve survival. Ketogenic diet is emerging as an attractive option in countering obesity‐related tumor‐promoting factors, as it is associated with weight loss as well as a reduction in insulin resistance and inflammation. Ketogenic diet can also deprive cancer cells of glucose, a fuel source that is predominantly used by many cancer lines through aerobic glycolysis in the setting of dysregulated mitochondria. Current manuscript reviews the theoretical benefits for use of ketogenic diet in cancer as well as the data available from clinical trials.