The current Western diet figures centrally in the pathogenesis of several chronic diseases such as obesity, type 2 diabetes, cardiovascular disease and the emerging major health problem nonalcoholic fatty liver disease, all of them negatively impacting on life expectancy. This type of diet is represented by a high calorie uptake, high glycemic load, high fat and meat intake, as well as increased consumption of fructose. On the contrary, a simplified way of eating healthily by excluding highly-processed foods, is presumed to be the Paleolithic diet (a diet based on vegetables, fruits, nuts, roots, meat, organ meats) which improves insulin resistance, ameliorates dyslipidemia, reduces hypertension and may reduce the risk of age-related diseases. The diet is the foundation of the treatment of obesity- and type 2 diabetes-related nonalcoholic fatty liver disease and a diet similar to those of pre-agricultural societies may be an effective option. To lend sufficient credence to this type of diet, well-designed studies are needed.