Assessment of maximal fat oxidation during exercise: A systematic review

Abstract

Maximal fat oxidation during exercise (MFO) and the exercise intensity eliciting MFO (Fatmax) are considered biological markers of metabolic health and performance. A wide range of studies have been performed to increase our knowledge about their regulation by exercise and/or nutritional intervention. However, numerous data collection and analysis approaches have been applied, which may have affected the MFO and Fatmax estimation. We aimed to systematically review the available studies describing and/or comparing different data collection and analysis approach factors that could affect MFO and Fatmax estimation in healthy individuals and patients. Two independent researchers performed the search. We included all original studies in which MFO and/or Fatmax were estimated by indirect calorimetry through an incremental graded exercise protocol published from 2002 to 2019. This systematic review provides key information about the factors that could affect MFO and Fatmax estimation: ergometer type, metabolic cart used, warm‐up duration and intensity, stage duration and intensities imposed in the graded exercise protocol, time interval selected for data analysis, stoichiometric equation selected to estimate fat oxidation, data analysis approach, time of the day when the test was performed, fasting time/previous meal before the test, and testing days for MFO/Fatmax and maximal oxygen uptake assessment. We suggest that researchers measuring MFO and Fatmax should take into account these key methodological issues that can considerably affect the accuracy, validity, and reliability of the measurement. Likewise, when comparing different studies, it is important to check whether the above‐mentioned key methodological issues are similar in such studies to avoid ambiguous and unacceptable comparisons.

Association of sedentary and physical activity time with maximal fat oxidation during exercise in sedentary adults

“…Further, although the graded exercise protocol used to assess MFO and Fat max was similar in both studies, Venables et al established a fasting time of 4 hours before starting the test, and used measured-values data analysis to estimate MFO and Fat max , whereas in the present work a fasting time of 5-6 hours was established and 3rd polynomial curve analysis used to estimate MFO and Fat max , in agreement with the most updated methodological consensus 29,36. Finally, Venables et al made no adjustment for VO 2 max, which is known to play a key role.…”

“…[13][14][15]18,[28][29][30]37 However, other authors suggest that 3 minutes might not be long enough to reach a steady metabolic state in very sedentary patients, which would affect any estimate of MFO and Fat max . It is noteworthy that the assessment of sedentary time and PA, 27 as well as the estimation of MFO and Fat max 29,36 were, however, performed in keeping with the latest methodological consensus. It has recently been proposed that there is diurnal variation in MFO, 28 which if true could have had an impact on the present results.…”

Association between sleep quality and time with energy metabolism in sedentary adults

“…A walking graded test on a treadmill (H/P/cosmos pulsar, H/P/cosmos sports & medical GmbH, Nussdorf-Traunstein, Germany) was performed to calculate MFO and FATmax following a previously validated methodology 35 . Briefly, the protocol started assessing the maximal walking speed of each participant [35][36][37] . After ~3 minutes resting, the walking graded test started with a 3-minute warm up at 3.5 km/h.…”

“…Maximal carbohydrate oxidation was not included in the analyses since it is not a key factor of energy metabolism during exercise 39 . Indeed, our recent systematic review has analyzed a total of 112 studies which included data about fuel oxidation during exercise 37 . None of those studies reported maximal carbohydrate oxidation during exercise.…”

Ultra Trail Performance is Differently Predicted by Endurance Variables in Men and Women

“…Subsequently, VO 2 , VCO 2 and ventilation data were averaged over the last 60 s of each 2-min stage and stoichiometric equations described by Frayn [22] were used to calculate fat oxidation rates with the assumption that urinary nitrogen excretion was negligible. Fat oxidation rates were then plotted against the relative exercise intensity ( %VO 2 peak) and a third-degree polynomial regression was used to determine maximal fat oxidation (MFO) and the exercise intensity eliciting MFO (FAT max ) for each participant [23]. MFO was normalized to lean body mass (mg/min/kg LBM).…”