title: Effects of Twenty Days of the Ketogenic Diet on Metabolic and Respiratory Parameters in Healthy Subjects.
abstract: The effects of the ketogenic diet (KD) on weight loss, metabolic, and respiratory parameters were investigated in healthy subjects.
  
  
  
  Thirty-two healthy subjects were randomized into two groups. The KD group followed a ketogenic diet for 20 days (KD t 0-t 20), then switched to a low-carbohydrate, no-ketogenic diet for 20 days (KD t 20-t 40), and finally was on a Mediterranean diet (MD) for 2 more months (KD t 40-t 2m). The MD group followed a MD for 20 days (MD t 0-t 20), then followed a MD of 1400 kcal over the next 20 days (MD t 20-t 40), and completed the study with the MD for 2 months (MD t 40-t 2m). Body weight, body fat, respiratory rate, and respiratory gas parameters (including respiratory exchange ratio (RER) and carbon dioxide end-tidal partial pressure (PETCO2), oxygen uptake (VO2), carbon dioxide production (VCO2), and resting energy expenditure (REE)) were measured at each point.
  
  
  
  A significant decrease (p < 0.05) in RER was observed after 20 and 40 days in the KD group, but not in the MD group. In the KD group, significant reductions were observed for both carbon dioxide output and PETCO2, however, there was no significant change in VO2, VCO2, and REE. While both diets significantly decreased body fat mass, the KD diet overall proved to have a higher percentage of fat loss versus the MD diet.
  
  
  
  The KD may significantly decrease carbon dioxide body stores, which may theoretically be beneficial for patients with increased carbon dioxide arterial partial pressure due to respiratory insufficiency or failure.
authors.affiliation: Department of Biomedical Sciences, University of Padova, 35131, Padua, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Rubini
authors.affiliation: Department of Biomedical Sciences, University of Padova, 35131, Padua, Italy.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Bosco
authors.affiliation: Department of Biomedical Sciences, University of Padova, 35131, Padua, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Lodi
authors.affiliation: Department of Biomedical Sciences, University of Padova, 35131, Padua, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Cenci
authors.affiliation: Department of Biomedical Sciences, University of Padova, 35131, Padua, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Parmagnani
authors.affiliation: Biomedical Engineering Laboratory, University of Athene, 15773, Athens, Greece.
authors.forename: Keith
authors.initials: K
authors.lastname: Grimaldi
authors.affiliation: The Institute for Human Performance, SUNY Upstate Medical University, Syracuse, NY, 13210, USA. Yangz@upstate.edu.
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhongjin
authors.affiliation: Department of Biomedical Sciences, University of Padova, 35131, Padua, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Paoli
mesh_terms: D000273:Adipose Tissue / Q000187:drug effects; D000328:Adult; D001835:Body Weight / Q000187:drug effects; D031204:Caloric Restriction; D002245:Carbon Dioxide / Q000378:metabolism*; D050528:Diet, Carbohydrate-Restricted; D055423:Diet, Ketogenic; D038441:Diet, Mediterranean; D004734:Energy Metabolism / Q000187:drug effects; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008875:Middle Aged; D010101:Oxygen Consumption / Q000187:drug effects; D010313:Partial Pressure; D010936:Plant Extracts / Q000494:pharmacology; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D056152:Respiratory Rate / Q000187:drug effects
chemical_list: D010936:Plant Extracts; D002245:Carbon Dioxide
keywords: Ketogenic diet; Metabolism; Respiration parameters; Resting energy expenditure