Dietary Protein Restriction Reverses Metabolic Dysfunction in Patients with the Metabolic Syndrome, Randomised Controlled Trial

Background: Dietary restriction (DR) reduces adiposity and improves metabolism in patients with one or more symptoms of the metabolic syndrome. Nonetheless, it remained elusive whether the benefits of DR in humans are mediated by calorie or nutrient restriction. Methods: Here we subjected 21 individuals diagnosed with the metabolic syndrome to short-term (i.e., 27-days) caloric restriction (CR; n = 11) or isocaloric dietary protein restriction (PR; n = 10) and compared the metabolic outcomes of the interventions. Findings: Like CR, PR promoted weight loss due to reduction in adiposity, and reduced blood glucose, lipid levels and blood pressure in these individuals. Hence, a reduction in calorie intake is not necessary to confer the metabolic benefits of DR. Instead, a reduction in protein intake with a mild increase in carbohydrate intake to maintain the caloric balance of the diet is sufficient to improve metabolic control in patients with the metabolic syndrome. Interpretation: Because PR is a less drastic food intervention to be conducted, it has a greater potential to be used as an adjuvant therapy to treat the metabolic syndrome. Trial Registration: This study is registered at the Brazilian Clinical Trials, ensaiosclinicos.gov.br, number RBR-3HKNRW. Funding Statement: This work was supported by grant 2015/12133-0 and 2017/01184-9 of Sao Paulo Research Foundation (FAPESP). Declaration of Interests: The authors declare they have no competing financial interests. Ethics Approval Statement: This study was approved by the Research Ethics Committee of the Clinics Hospital of Ribeirao Preto and by the Plataforma Brasil. The Helsinki Declaration Guidelines have been followed and the reports in this article are aligned with the CONSORT standards. All participants were informed about the procedures and signed a study consent form.