RESUMEN
BACKGROUND & AIMS: Oral ketone supplements may mimic the beneficial effects of endogenous ketones on energy metabolism as ß-hydroxybutyrate has been proposed to increase energy expenditure and improve body weight regulation. Therefore, our objective was to compare the effects of a one-day isocaloric ketogenic diet, fasting and supplementation with ketone salts on energy expenditure and appetite perception. METHODS: Eight healthy young adults (4 women, 4 men, age 24 ± 3 years, BMI 24.3 ± 3.1 kg/m2) participated in a randomized cross-over trial with four 24 h-interventions in a whole room indirect calorimeter at a physical activity level of 1.65: (i) total fasting (FAST), (ii) isocaloric ketogenic diet (3.1% energy from carbohydrates (CHO), KETO), (iii) isocaloric control diet (47.4% energy from CHO, ISO), and (iv) ISO supplemented with 38.7 g/d ketone salts (exogenous ketones, EXO). Effects on serum ketone levels (15 h-iAUC), energy metabolism (total energy expenditure, TEE; sleeping energy expenditure, SEE; macronutrient oxidation) and subjective appetite were measured. RESULTS: Compared to ISO, ketone levels were considerably higher with FAST and KETO and little higher with EXO (all p > 0.05). Total and sleeping energy expenditure did not differ between ISO, FAST and EXO whereas KETO increased TEE (+110 ± 54 kcal/d vs. ISO, p < 0.05) and SEE (+201 ± 90 kcal/d vs. ISO, p < 0.05). CHO oxidation was slightly decreased with EXO compared to ISO (-48 ± 27 g/d, p < 0.05) resulting in a positive CHO balance (p < 0.05). No differences between the interventions were found for subjective appetite ratings (all p > 0.05). CONCLUSION: A 24 h-ketogenic diet may contribute to maintain a neutral energy balance by increasing energy expenditure. Exogenous ketones in addition to an isocaloric diet did not improve regulation of energy balance. CLINICAL TRIAL REGISTRATION: NCT04490226 https://clinicaltrials.gov/.
Asunto(s)
Dieta Cetogénica , Masculino , Adulto Joven , Humanos , Femenino , Adulto , Cetonas , Voluntarios Sanos , Sales (Química) , Metabolismo Energético/fisiología , AyunoRESUMEN
OBJECTIVE: The aim of this study was to validate two new whole-room indirfect calorimeters according to Room Indirect Calorimetry Operating and Reporting Standards (RICORS 1.0). METHODS: For technical validation, 16 propane combustion tests were performed to determine accuracy and precision of energy expenditure (EE) and ventilation rates of oxygen (VO2 ), carbon dioxide (VCO2 ), and respiratory exchange ratio (VCO2 /VO2 ). For biological validation, eight participants (mean [SD], age 24.1 [2.5] years; BMI 24.3 [3.1] kg/m2 ) underwent four 24-hour protocols under highly standardized conditions: (1) isocaloric sedentary, (2) fasting sedentary, (3) isocaloric active, and (4) fasting active. Reliability (coefficients of variation [CV]) and minimal detectable changes (MDC) were calculated for 24-hour EE, sleeping metabolic rate (SMR), physical activity energy expenditure (PAEE), thermic effect of food (TEF), and macronutrient oxidation rates. RESULTS: Technical validation showed high reliability and recovery rates for VO2 (0.75% and 100.8%, respectively), VCO2 (0.49% and 100.6%), and EE (0.54% and 98.2%). Biological validation revealed CV and MDC for active conditions of 1.4% and 4.3% for 24-hour EE, 1.7% and 5.9% for SMR, and 30.2% and 38.4% for TEF, as well as 5.8% and 10.5% for PAEE, respectively. Mean CV and MDC for macronutrient oxidation rates were 9.9% and 22.9%, respectively. CONCLUSIONS: The precision of 24-hour EE and SMR was high, whereas it was lower for PAEE and poor for TEF.