Dieta restrita em carboidratos versus dieta restrita em calorias e lipídios para perda de peso e controle de fatores de risco cardiovascular em adultos obesos: revisão sistemática com metanálise de ensaios clínicos aleatórios

Abstract

Nutritionists must incorporate scientific evidence into their therapeutics; however, this activity requires knowledge of scientific evidence and its hierarchy in order to prevent wrong procedures to be used. Systematic reviews and meta-analyses appear as the best tool to summarize the available evidence on any particular topic, answering concise and narrow research questions. The dietary restriction of carbohydrates is a therapeutic seldom used in the nutrition field, despite some published clinical trials which shows that it can be used as an additional tool against obesity. However, certain gaps have not been filled with regard to this therapy. The present study aimed to perform a systematic review with meta-analysis of randomized controlled trials, to evaluate whether adults assigned to a ketogenic diet highly restricted in carbohydrates lose more weight and achieve better metabolic control of cardiovascular risk factors, when compared to individuals allocated to a conventional diet restricted in calories and fat, in the long-term, defined as 12 or more months of follow up. Hence, this work was divided into two distinct parts: the first is a narrative review chapter, where we explain the importance of systematic reviews and meta-analyses on the incorporation of scientific evidence into the clinical practice of the nutritionist. The second part is an article with the results of a meta-analysis of 13 randomized clinical trials, included through systematic search of electronic databases. The main results were that the individuals assigned to the ketogenic diet highly restricted in carbohydrates showed significantly greater weight loss and greater reduction in triglycerides and diastolic blood pressure, while exhibit increases in the levels of both HDL and LDL, when compared with individuals allocated to a conventional diet restricted in calories and fat, in long-term. Despite the statistical significance, the interpretation of these findings requires caution regarding its clinical significance. Through this meta-analysis it can be concluded that the ketogenic diets severely restricted in carbohydrates are, at least, as effective as the conventional diets restricted in calories and fat against obesity in the long term and can be used as na alternative tool in this context.