Cancer is multicausal disease associated with accumulation of multiple DNA mutations that cause a deregulation of cell proliferation and differentiation, loss of normal tissue organization, and eventually tissue invasion and dislocation to distant sites. It is known as a multifactorial disease, which means its prevalence can be caused not only by one, but a number of factors. Lifestyle factors, including diet have long been “recognized as potentially important determinants of cancer risk” (1) Researches of the past few years have suggested a close correlation between obesity, insulin resistance, diabetes, and cancer formation. Hyperinsulinaemia is believed to increase the risk of many cancers, including breast and colorectal cancer (2). Moreover, pancreatic cancer, which has a very poor prognosis with the highest mortality, has a higher risk of occurrence in individuals with frequent consumption of sugar, most importantly fructose. New studies have shown strong relationship between diabetes and certain types of cancer, being lifestyle crucial in the prevention and development of both diseases. Besides physical inactivity, diets with high glycemic index and glycemic load are believed to strongly contribute in the development of diabetes as well as cancer due to mechanisms like hyperglycemia, hyperinsulinemia and inflammation. Just recently, a close association between diabetes treatment and its effect on cancer has also emerged. Studies show evidence that antidiabetic therapy using drugs like metformin is associated with a lower risk of cancer, but exogenous insulin is associated with an increased cancer risk. Finally, a huge amount of data suggests that cutting back on calorie intake is very effective in preventing malignant disease. Mediterranean and ketogenic diet are strongly advised for patients under high risk of diabetes and cancer. Moreover, ketogenic diet has been shown to decrease the volume of tumors, being strongly recommended for cancer patients.