In the last years plant-based diets have been regarded as beneficial for the prevention of widely spread diseases, such as cancer. On the opposite, frequent ingestion of animal products, enriched in proteins and fats, and often causative of decreased insulin sensitivity, higher serum cholesterol and insulin like growth factor (IGF)-1 levels and increased abdominal obesity, is often directly associated to the risk of several cancer types, such as colorectal, breast and prostate cancers, all known to be linked to insulin resistance. Here, the role of plant vs animal-based diets in the prevention and regression of insulin resistance-related cancers is discussed. Despite some divergences, overall the reported studies suggest that plant-based dietetic regimens might be protective against these types of cancers, opposite to animal-based dietary patterns. Additionally, as the cooking process normally alter the availability of phytonutrients and determine the formation of several food toxins, the possible beneficial effect associated to the consumption of raw plant-derived vs cooked foods is discussed.