Time-restricted Feeding Increases Fat Oxidation Rate But Not Affect Postprandial Lipemia: a Crossover Trial
Phase: NA
Conditions: Time-restricted Feeding, Postprandial Lipemia
Sponsor: National Taiwan Sport University

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Time-restricted feeding increases fat oxidation rate but not affect 
postprandial lipemia: a crossover trial 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Official title: National Taiwan University of Sport  
Date of the document: 02/02/2022 
 
 
 
 
Dr Chih-Hui Chiu 
Graduate Program in Department of Exercise Health Science,  
National Taiwan University of Sport  
No.16, Sec. 1, Shuang-Shih Rd.,  
Taichung 404, Taiwan  
Tele: +886-4-2221-3108 ext 3486 
Fax: +886-4- 2225-6937 
E-mail: chiuch@ntus.edu.tw. 
 
 
 
 

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Abstract 
Background: Studies have revealed that time-restricted feeding affects the fat 
oxidation rate; however, its effects on the fat oxidation rate and hyperlipidemia 
following high-fat meals are unclear. This study investigated the effects of 5-day time-
restricted feeding on the fat oxidation rate and postprandial lipemia following high fat 
meals. Methods: In this random crossover experimental study, eight healthy male 
adults were included each in the 5-day time-restricted feeding trial and the control trial. 
The meals of the time-restricted feeding trial were provided at 12:00, 16:00, and 20:00. 
The meals of the control trial were provided at 08:00, 14:00, and 20:00. The contents 
of the meals of both trials were the same, and the calories of the meals met the 24-hour 
energy requirement of the participants. After 5 days of the intervention, the participants 
consumed high-fat meals on the sixth day, and their physiological changes were 
determined.  
 
Key words: intermittent fasting, oral fat tolerance test, fat oxidation 
 
 
 
 
 

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Introduction 
Consuming high-fat meals increases the triglyceride (TG) level in blood plasma. 
Studies have discovered that large increases in postprandial TG concentration lead to 
high risks of cardiovascular diseases and metabolic syndrome 1. Compared with the 
fasting TG concentration, the postprandial TG concentration is a more precise predictor 
of the risks of cardiovascular diseases and metabolic syndrome 2. Consuming high-fat 
meals increases the levels of biochemical substances in blood plasma, such as TG, free 
fatty acids, and remnant cholesterol. Studies have reported that these biochemical 
substances are major risk factors for metabolic syndrome, atherosclerosis, myocardial 
infarction, and coronary heart disease, all of which are associated with high mortality 
3,4. The high TG level after the consumption of high-fat meals can last for 6–8 hours. 
As three meals daily are typically consumed by the general population, high levels of 
TG may be constantly occurring in the body. Therefore, investigating methods to 
reduce the high TG level after eating high-fat meals is crucial for reducing the 
development of metabolic syndrome. 
Studies have demonstrated that a single session of endurance exercise can 
effectively reduce the TG level after the consumption of high-fat meals 5-8. In addition, 
performing a single session of endurance exercise 8 hours before meals can effectively 
reduce the increase in TG after the consumption of high-fat meals, and the effect can 
last for 48–60 hours 9,10. Endurance exercises effectively reduce the increase in 
postprandial TG because they increase lipoprotein lipase activity and insulin sensitivity, 
and they reduce the release of very low-density lipoprotein by the liver 10. Recent 
studies have shown that increasing the fat oxidation rate after eating high-fat meals is 
crucial for reducing the postprandial TG level 11,12; however, the results have remained 
inconsistent. Some studies have described that performing high-intensity interval 

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training is positively correlated with decreases in the postprandial TG level 13, whereas 
other studies have discovered that the increased fat oxidation rate following high-fat 
meals did not affect the postprandial TG level 14. 
Studies have discovered that time-restricted feeding can improve insulin sensitivity 
15, increase the fat oxidation rate 16, and decrease the fasting TG level 17. However, 
whether time-restricted feeding can exert health benefits in terms of effectively 
reducing the increase in the TG level following high-fat meals remains unclear. This 
study investigated the effects of 5-day time-restricted feeding on the fat oxidation rate 
and postprandial lipemia after the consumption of high-fat meals. 
 
Methods 
 
Participants 
This study recruited eight healthy male adults as research participants (age: 22 ± 
1.3 yr, height: 170.1 ± 4.7 cm, weight: 75.4 ± 17.5 kg). All the participants had not 
undergone physical training; they did not exercise regularly; and they did not have any 
diseases that would prevent them from performing exercises, such as high blood 
pressure, hyperlipidemia, heart disease, joint disease, and osteoporosis. All the 
participants fully understood the experimental process before experiment initiation and 
were notified of the possible risks; they agreed to the terms of the experiment and 
provided their written consent. A similar number of participants and a similar 

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recruitment method have been employed by this research team in the past. This study 
was approved by the Institutional Review Board of Jen-Ai Hospital (110-10) in Taiwan. 
 
Design 
    This study used a crossover design for the experiment. The participants were 
divided into the time-restricted feeding trial and the control trial; the participants in the 
control trial did not practice intermittent fasting methods. The participants of both trials 
consumed the same meals for 5 days. The time-restricted feeding group used the 16:8 
methods to practice intermittent fasting. The meals were provided at 12:00, 16:00, and 
20:00. The meals of the control group were provided at 08:00, 14:00, and 20:00, but the 
consumption time was not limited. On the morning of the sixth day, all participants 
returned to the laboratory to consume high-fat meals, and their TG blood levels after 
the meal was determined. The participants were randomly assigned to different arms of 
the study to receive different treatments, and an interval of at least 14 days was 
maintained between the tests to avoid any effects of the preceding test on the succeeding 
test. Studies have discovered that 4 days of intermittent fasting effectively increased the 
fat oxidation rate and reduced blood glucose 18,19. Therefore, 5 days of intermittent 
fasting should provide sufficient intervention time to stimulate fat oxidation rate 
changes. 

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Protocol 
Pretest 
In the pretest, gas analyzers (Vmax Series 29C, Sensor Medics, CA, USA) were 
used to assess the energy consumption of the participants while they were resting and 
performing nonmaximal intensity exercises for precisely calculating the daily calorie 
consumption of each participant. After the participants arrived at the laboratory, they 
wore heart rate monitors (Polar, Finland), and their energy consumption was examined 
using gas analyzers. Next, they quietly rested for 20 minutes in the supine position, and 
their resting heart rate and energy consumption were recorded. They then performed 
nonmaximal intensity exercises for measuring their energy consumption during low-
intensity activities. The participants stood on a treadmill with a slope of 0° for 10 
minutes to record their energy consumption during standing. The participants then 
walked or ran on the treadmill at five speeds, namely 1, 2, 3, 4, and 5 miles per hour. 
The participants maintained each speed for 3 minutes for examining the relationship 
between the energy consumption and heart rate of the participants during low-intensity 
activities. 
After the pretest, the participants were asked to perform their normal daily life 
activities while wearing the heart rate monitor; their heart rates were recorded for 24 

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hours. The 24-hour heart rate, the regression curve of the heart rate, and energy 
consumption calculated in the pretest were be used to calculate the total energy 
consumption of the participants. In the experiment, meals were adjusted so that the total 
calories of each meal met the 24-hour energy requirement of each participant. The 
method used to record energy consumption and the brand of heart rate monitors (Polar) 
used in this study have been described elsewhere 12,20,21. Moreover, 24-hour energy 
consumption was recorded the day before the experiment, and the calories of meals 
were adjusted to meet the 24-hour energy requirement of each patient. The same 
methods were repeated on the fifth day of the experiment to confirm the 24-hour energy 
consumption changes of the two trials. 
 
Formal Experiment 
    The experiment was conducted over 6 days. On the first day, the participants 
arrived at the laboratory at 08:00 and quietly rested for 20 minutes in the supine position; 
gas analyzers were used to record their energy consumption. Subsequently, the 
participants were randomly allocated to the time-restricted feeding trial or the control 
trial. The meals of the time-restricted feeding trial were provided at 12:00, 16:00, and 
20:00, and the participants were required to consume all the food during this time. The 
meals of the control trial were provided at 08:00, 14:00, and 20:00, but the consumption 

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time was not limited. In addition to regular meals, a snack with approximately 200 
calories was provided to the participants for consumption. The participants in the time-
restricted feeding trial were only allowed to consume the snack from 12:00 to 20:00, 
whereas no restrictions were imposed on the control trial for snack consumption. The 
meals of the participants were provided by dieticians. Based on the results of the pretest, 
the calories of each meal met the daily energy requirement of the participants. The 
macronutrient consumption for TRF and CON were listed in table 1. 
 
    After experiment completion on the fifth day, the participants returned to the 
laboratory on the eighth day from 08:00 to 09:00. They rested for 10 minutes in the 
supine position, and gas analyzers were used to collect the gas data of the participants 
for 20 minutes. Next, a catheter was inserted into the forearm of each participant to 
collect fasting blood samples. After blood sample collection, the participants were 
provided with a specific high-fat meal. The participants rested quietly in the laboratory 
for 4 hours, and their blood lipid changes during this period were observed. 
 
Oral fat tolerance test (OFTT） 
    All oral fat tolerance test (OFTT) meals were designed and provided by dieticians, 
as previously described 12,22,23. The meals included toast, butter, cheese, muesli, and 

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cream. For every kg of the body weight of the participant, the meal provided 1.2 g of 
fat, 1.1 g of carbohydrate, 0.33 g of protein, and 16.5 kcal of energy. The nutritional 
information was obtained from the nutritional facts on food packages. During the 
experiment, the participants were required to consume the OFTT meal within 15 
minutes. 
 
Blood collection 
In the experiment, a catheter (Venflon 20G, Sweden) was inserted into the vein of 
the forearm, and a three-way stopcock (Connecta Ltd., Sweden) was used to collect 10 
mL of blood each time. Blood was collected before meals, 30 minutes after meals, and 
every hour after meals up to the fourth hour. After each session of blood collection, 10 
mL of isotonic saline water was used to clean the catheter to avoid blood clotting in the 
catheter. 
The collected blood was immediately placed in blood collection tubes containing 
ethylenediaminetetraacetic acid. A cell counter was used to analyze the hematocrit 
(Sysmax KX-21N, Kobe, Japan). After the analysis, the blood was centrifuged for 20 
minutes at 500 × g at 4℃. Blood plasma was obtained and was immediately placed in 
a −80℃ refrigerator for preservation and future biochemical analysis. 
Blood biochemical analysis 

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TG, blood glucose, free fatty acid, and glycerol levels in blood were analyzed 
using an automated biochemistry analyzer (7020, Hitachi, Japan) and commercial 
reagents (GOD-PAP method, Randox, Ireland). The insulin concentration in blood 
plasma was analyzed using a chemiluminescence immunoassay analyzer (Elecsys 2010, 
Roche Diagnostics, Basel, Switzerland) and commercial reagents (Roche Diagnostics). 
The fat and carbohydrate oxidation rates were calculated using the following formula24: 
Fat oxidation (g/min) = 1.695 × VO2 − 1.701 × VCO2   
Carbohydrate oxidation (g/min) = 4.585 × VCO2 − 3.226 × VO2 
 
Statistical Analysis 
    All the data in this study are presented as average ± standard deviation. First, the 
normality of the data was tested using the Shapiro–Wilk test. The fasting fat oxidation 
rate, blood biochemical values, and areas under the fat oxidation rate curve and the TG 
curve were analyzed using the paired sample t test. The postprandial fat oxidation rate 
and blood biochemical values were analyzed using two-way ANOVA with repeated 
measures. If the data were significant, the Bonferroni method was used to perform post 
hoc comparisons. Using G*power 3, to achieve an alpha value of 5% and a power of 
0.8, the sample size of eight was considered sufficient for this study. The signiﬁcance 
level was set atα < 0.05.