Determination of the exercise intensity that elicits maximal fat oxidation in individuals with obesity

Abstract

Maximal fat oxidation (MFO) and the exercise intensity that elicits MFO (Fat) are commonly determined by indirect calorimetry during graded exercise tests in both obese and normal-weight individuals. However, no protocol has been validated in individuals with obesity. Thus, the aims were to develop a graded exercise protocol for determination of Fat in individuals with obesity, and to test validity and inter-method reliability. Fat oxidation was assessed over a range of exercise intensities in 16 individuals (age: 28 (26-29) years; body mass index: 36 (35-38) kg·m; 95% confidence interval) on a cycle ergometer. The graded exercise protocol was validated against a short continuous exercise (SCE) protocol, in which Fat was determined from fat oxidation at rest and during 10 min of continuous exercise at 35%, 50%, and 65% of maximal oxygen uptake. Intraclass and Pearson correlation coefficients between the protocols were 0.75 and 0.72 and within-subject coefficient of variation (CV) was 5 (3-7)%. A Bland-Altman plot revealed a bias of -3% points of maximal oxygen uptake (limits of agreement: -12 to 7). A tendency towards a systematic difference (p = 0.06) was observed, where Fat occurred at 42 (40-44)% and 45 (43-47)% of maximal oxygen uptake with the graded and the SCE protocol, respectively. In conclusion, there was a high-excellent correlation and a low CV between the 2 protocols, suggesting that the graded exercise protocol has a high inter-method reliability. However, considerable intra-individual variation and a trend towards systematic difference between the protocols reveal that further optimization of the graded exercise protocol is needed to improve validity.

Effects of Acute Whole-Body Vibration Practice on Maximal Fat Oxidation in Adult Obese Males: A Pilot Study

“…Regarding the graded incremental exercise test, even if cycle ergometer has been more often used for CPET tests in obese subjects, we chose the treadmill because it reflects better the walking exercise that subjects might perform as regular unsupervised PA in an almost daily routine. Our MFO results were higher than those reported by other studies in obese subjects (MFO ranging from 0.25 to 0.4 g/min) [9,35]. These differences might by justified by the different graded exercise protocol, and nutritional status of the subjects during the experimental test.…”

Reduced Fat Oxidation During Exercise in Post-Menopausal Overweight-Obese Women with Higher Lipid Accumulation Product Index

“…We recognize this clear limitation of our study. However, adding 1 extra minute to each stage would have extended the total duration of the protocol by 5-6 min, which in these subjects could also have affected VO2 and VCO2, especially at the last steps [37]. Future studies should be performed to analyze the impact of the stages length of exercise test on substrate oxidation in obese individuals with different grades of metabolic health.…”

Contextualising Maximal Fat Oxidation During Exercise: Determinants and Normative Values

“…The first reliability study of the Fat max protocol described above reported a coefficient of variation (CV) of 9.6% for Fat max in a cohort of overnight fasted moderately-trained males with 24-h pre-trial dietary repetition (Achten and Jeukendrup, 2003a ). Interestingly, a similar study reported a CV of just 3% for Fat max and 11% for MFO (Dandanell et al, 2017b ). These CVs are similar to those for MFO measured in sedentary cohorts using 4–5 pre-defined submaximal workloads based on prior assessment of maximal aerobic power (Gmada et al, 2012 ; Marzouki et al, 2014 ).…”