ABSTRACT Countless strategies have been proposed to change dietary patterns to promote weight loss. Many of these strategies are controversial, with questions of effectiveness and possible negative consequences to health, even if weight loss effects are achieved. Ketogenic diets, with or without calorie restrictions, are framed in this context. In the present systematic review, evidence on ketogenic diets for weight loss was investigated. Studies on ketogenic diet with or without calorie restriction related to weight loss published between 2012 and 2017 were selected from MEDLINE, Scielo and Web of Science databases. Results show there is a lack of knowledge on specific physiological mechanisms involved in the ketogenic diet. Much of the evidence published, despite showing specific effects on weight loss, BMI and fat percentage reduction, did not precisely assess its effects on specific physiological and biochemical parameters, mainly on the hepatic, cardiac and renal tissues. We conclude that strategies to control overweight and obesity do not necessarily need to impose restrictions on certain nutrients, especially carbohydrates, or increase the intake of food groups whose excessive consumption has been associated with different pathologies.