Effects of Twenty Days of the Ketogenic Diet on Metabolic and Respiratory Parameters in Healthy Subjects

Purpose The effects of the ketogenic diet (KD) on weight loss, metabolic, and respiratory parameters were investigated in healthy subjects. Methods 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 (PETCO 2 ), oxygen uptake (VO 2 ), carbon dioxide production (VCO 2 ), and resting energy expenditure (REE)) were measured at each point. Results A significant decrease ( p