Enhancement of Fat Oxidation during Submaximal Exercise in Sedentary Persons: Variations by Medium‐Chain Fatty Acid Composition and Age Group

Abstract

Previous studies in recreational and trained athletes aged mostly in their 20s have reported that short‐term ingestion of medium‐chain triacylglycerols (MCT) enhances fat oxidation (FAO) during submaximal exercise. However, whether the FAO‐enhancing effect of MCT with a different composition of medium‐chain fatty acids (MCFA) occurs in older sedentary persons is unclear. The present study investigated the effect of MCT ingestion with different proportions of MCFA in sedentary participants in their 40's and 50's. Participants ingested 0 g of MCT (control), 6 g of octanoic acid‐rich MCT (OAR), or 6 g of decanoic acid‐rich MCT (DAR) for 14 days separated by a 14‐day washout period in random order. Cumulative FAO (Fcv) during submaximal, fixed, and incremental exercise was evaluated at workload from 20 W to the appearance of a ventilation threshold (VT). During the 20 W fixed‐load exercise, Fcv was significantly (p < 0.05) higher in the OAR than in the control. At appearance of VT, intervention effect of power output was significantly higher in the OAR and DAR than in the control. In a subgroup analysis by age, intervention effects of maximal FAO rate and oxygen uptake in the upper age subgroup were higher in the OAR and DAR than in the control. In a pooled analysis with age subgroup and diet, the integrated pooled estimate of Fcv during submaximal exercise was significantly higher in 6 g of MCT ingestion than 0 g ingestion. Our data show that the effect of MCT might differ depending on the age group and the proportion of MCFA, while MCT could enhance FAO during submaximal exercise.

Effect of Continuous Ingestion of 2 g of Medium-Chain Triglycerides on Substrate Metabolism during Low-Intensity Physical Activity

“…However, there are many issues to be considered, including the fact that continuing a high-fat diet is detrimental because it involves a drastic change in diet, and even if it can be continued, it will increase body weight and body fat, which is concerning [ 30 ]. On the other hand, it has been shown that the application of 6 g of MCTs per day causes increased fat burning in skeletal muscle even in those on a normal fat diet, with or without exercise habits [ 10 , 11 , 12 ]. Furthermore, this study showed that a continuous ingestion of only 2 g of MCTs per day can enhance fat burning during low-intensity physical activity.…”

“…Based on the mean difference and standard deviation of the cumulative fat oxidation and the maximum fat oxidation rate during low-intensity physical activity after ingestion of 6 g of MCTs for 2 weeks compared with the control [ 11 ], the number of subjects required for the study was estimated to be 18 or more and 23 or more. While the ingested amount of MCTs was one-third of that in the estimated study, a highly sensitive mass spectrometer was used to measure oxygen uptake and carbon dioxide production, which are the basic values for calculating fat oxidation, so the required number of subjects was judged to be slightly higher than the estimated number, 27 subjects were set, and so the target number of subjects was set at 30, based on the expectation that 10% of the subjects would be ineligible for analysis.…”

“…MCFAs broadly refer to straight-chain saturated fatty acids consisting of 6–12 carbon chains, but research on physiological functions has focused on octanoic acid (C8) and decanoic acid (C10), or on medium-chain triglycerides (MCTs) consisting of C8 and C10. Continuous ingestion of MCTs has been reported to promote fat utilization during moderate-intensity exercise in recreational athletes [ 10 ] and during low-intensity daily activities in normal-weight subjects [ 11 , 12 ], and has been shown to reduce body weight and body fat [ 13 , 14 ].…”

“…The effect of continuous MCTs ingestion on fat oxidation during physical activity has been tested in normal weight subjects, but the effect on those with higher BMI is unknown. Although studies have been conducted with the ingestion dose of MCTs set at 6 g per day [ 11 , 12 ], if it can be shown that MCTs are effective even at lower doses then the burden of continuous ingestion will be reduced.…”

Nutritional and technological aspects of vegetable oils that stand out for the prevalence of medium-chain triacylglycerides: A review

“…MCFAs induce much greater increase in the activity of the muscle oxidative enzyme (Montgomery et al, 2019) (Thevenet et al, 2016). A study carried out with sedentary individuals in the age group 40 and 60 years who received a diet rich in medium-chain fatty acids showed that exercising increases and improves the aerobic capacity in terms of oxygen transport and cardiac output capacity (Nosaka et al, 2020).…”