A comparative analysis of energy expenditure and substrate metabolism in male university students with overweight/obesity: Tabata vs HIIT and MICT

Introduction Exploring the energy expenditure and substrate metabolism data during exercise, 10-minute recovery, and 20-minute recovery phases in Tabata, HIIT(High-Intensity Interval Training), and MICT(Moderate-Intensity Continuous Training). This study explores the scientific aspects of weight reduction strategies, examining energy expenditure and substrate metabolism from various training perspectives. The aim is to establish a theoretical foundation for tailoring targeted exercise plans for individuals within the population with overweight/obesity. Methods This study used an experimental design with fifteen male university students with overweight/obesity. Participants underwent random testing with Tabata, HIIT, and MICT. Tabata involved eight sets of 20 seconds exercise and 10 seconds rest, totaling 4 minutes. HIIT included four sets of power cycling: 3 minutes at 80% VO2max intensity followed by 2 minutes at 20% VO2max. MICT comprised 30 minutes of exercise at 50% VO2max intensity. Gas metabolism indices were continuously measured. Subsequently, fat and glucose oxidation rates, along with energy expenditure, were calculated for each exercise type. Results During both the exercise and recovery phases, the Tabata group exhibited a significantly higher fat oxidation rate of (0.27 ± 0.03 g/min) compared to the HIIT group (0.20 ± 0.04 g/min, p<0.05) and the MICT group (0.20 ± 0.03g/min, p<0.001). No significant difference was observed between the HIIT and MICT groups (p=0.854). In terms of energy expenditure rate, the Tabata group maintained a substantially elevated level at 5.76 ± 0.74kcal/min compared to the HIIT group (4.81 ± 0.25kcal/min, p<0.01) and the MICT group (3.45 ± 0.25kcal/min, p<0.001). Additionally, the energy expenditure rate of the HIIT group surpassed that of the MICT group significantly (p<0.001). Conclusion The study finds that male college students with overweight/obesity in both exercise and recovery, Tabata group has lower fat and glucose oxidation rates, and energy expenditure compared to HIIT and MICT groups. However, over the entire process, Tabata still exhibits significantly higher rates in these aspects than HIIT and MICT. Despite a shorter exercise duration, Tabata shows a noticeable “time-efficiency” advantage. Tabata can be used as an efficient short-term weight loss exercise program for male college students with overweight/obesity.


Introduction
In recent years, the improvement of living standards has brought about various health issues, with obesity being a global public health concern.The sedentary lifestyle and changes in dietary habits associated with socio-economic development have contributed to a rapid increase in global obesity rates (1).According to the World Obesity Federation's "World Obesity Atlas 2023" report, it is projected that over the next 12 years, more than 51% of the global population-exceeding 4 billion people -will be either obese or overweight.Research indicates that obesity is a significant risk factor for chronic diseases such as cardiovascular diseases, diabetes, and musculoskeletal disorders (2).The high prevalence of obesity significantly affects the health and societal development in China, making the scientific and efficient approach to weight loss a critical issue.
Traditional weight loss exercises often involve MICT (Moderate-Intensity Continuous Training), such as walking, brisk walking, running, and cycling, which has proven to be effective (3).However, the lengthy and monotonous nature of the exercise makes it challenging for many individuals with obesity to adhere to.In recent years, HIIT(High-Intensity Interval Training) has gained attention.Initially proposed by Reindell and Roskamm (4), HIIT has become popular among fitness enthusiasts.HIIT involves repeated cycles of high-intensity exercise interspersed with lowintensity exercise or rest periods with varying recovery times (5).Compared to traditional long-duration continuous exercise, HIIT has a relatively short exercise duration but higher intensity (6,7).HIIT is considered an exercise method that increases the metabolic rate and promotes fat consumption (8).The primary energy systems during HIIT are the phosphagen and glycolytic systems, with glucose being the main metabolic substrate.Therefore, the efficacy of HIIT in reducing fat is not solely due to the energy expenditure during exercise but also the significant aerobic demand fluctuations that enhance post-exercise metabolic rate and fat utilization (9).
However, traditional HIIT training still requires more than 20 minutes.This is where Tabata comes into play.Originating in Japan, Tabata involves 20 seconds of exercise, 10 seconds of rest, repeated for eight sets, totaling a 4-minute interval training session (10,11).Compared to HIIT and MICT, Tabata offers advantages such as a relatively short exercise duration, high enjoyment, unrestricted space requirements, and easy implementation, making it more accessible for individuals with overweight/obesity to adhere to.
Current research primarily focuses on the effects of different exercise modalities on body composition, body components, and weight loss.Many scholars have conducted comparative studies on the fitness effects of HIIT and MICT, finding that for the same energy expenditure, HIIT yields a greater increase in VO 2max [23.8% vs 19.3% (12), 15.8% vs 8.0% (13), 14% vs 7% (14)].Moreover, HIIT has been shown to reduce insulin and blood sugar levels, improve insulin sensitivity, and enhance the mechanisms of blood dynamics, metabolism, and endocrine factors involved in the pathogenesis of hypertension in healthy populations (13).The effects of HIIT are also superior to those of MICT for reducing total fat mass and abdominal fat mass, even with the same energy expenditure (15).
Physical exercise promotes browning of adipocytes, which is a transition from white adipose tissue to metabolically active brown adipose tissue.The characteristic of browning is an increase in the number of mitochondria and the dissipation of energy through heat generation, namely non shivering heat generation.Due to the large amount of energy consumed by brown adipose tissue in non shivering heat generation, this can lead to an overall increase in energy consumption.Physical exercise can promote more effective energy consumption in the body by activating these physiological processes.This is precisely why this study aims to provide new insights into the field of exercise and weight loss for obese individuals from the perspectives of energy expenditure and substrate metabolism through different exercise methods.
The debate over the superiority of weight loss effects between HIIT and MICT is a current hotspot.Although some studies suggest that HIIT is more effective for weight loss than MICT, due to differences in research methods and training programs, it is premature to conclude that HIIT is superior to MICT for weight loss (16,17).With the emergence of Tabata, a form of exercise with shorter duration and higher intensity compared to HIIT and MICT, further research is needed to determine its potential superior effects on weight loss.Therefore, this study aims to conduct experimental research on randomly selected individuals with overweight/obesity undergoing Tabata, HIIT, and MICT.The analysis will focus on substrate metabolism and energy expenditure data during the exercise and recovery phases of 10 and 20 minutes, comparing the fat oxidation rate, glucose oxidation rate, and energy expenditure rate of the three exercise modalities.The findings aim to provide a theoretical basis for the tailored development of training plans for overweight/obese individuals.

Subjects and methods
This study employed an experimental research design involving a cohort of randomly selected fifteen male university students with overweight/obesity.Initial assessments included maximal oxygen consumption tests to determine the power corresponding to 20% VO 2max , 50% VO 2max , and 80% VO 2max intensities on a stationary bicycle.Subsequently, participants underwent random Tabata, HIIT and MICT exercise tests, each separated by a 7-day interval.Continuous measurements of gas metabolism parameters were conducted during exercise and the 10-minute and 20-minute recovery periods.This data was then utilized to calculate the fat oxidation rate, glucose oxidation rate, and energy expenditure rate for each of the three exercise modalities.

Participants
Fifteen male university students with overweight/obesity were randomly selected for this study (mean ± standard deviation, age: 22.85 ± 2.40 years, height: 177 ± 5.64 cm, weight: 86.40 ± 4.80 kg, Body Fat Percentage(BFP): 24.82 ± 1.43%, BMI: 27.12 ± 1.48 kg/m 2 , Fat mass:21.33 ± 2.41 kg, lean mass:64.67 ± 3.07 kg).All participants had a BMI greater than 24 kg/m 2 , according to Chinese adult BMI standards (overweight BMI > 24 kg/m 2 , obesity BMI > 28 kg/m 2 ), indicating good physical condition.They reported no regular exercise habits, were non-smokers, and had no history of diabetes or metabolic disorders.Exclusion criteria included smokers, individuals with a history of diabetes or metabolic diseases.In the week preceding the experiment, participants refrained from intense physical activity, smoking, alcohol consumption, and the intake of caffeinated beverages or medications for 48 hours prior to testing.Dietary habits were recorded for the week before the experiment, focusing on normal daily meals with avoidance of high-fat and high-sugar foods.During the experiment, participants were instructed to maintain the same dietary structure and quantity as the previous week to eliminate dietary interference.Adequate sleep was encouraged, with participants advised against staying up late or having irregular sleep schedules to minimize potential impacts on the experiment.Before testing, participants were fully informed about the purpose and procedures of the study and provided informed consent.

Experimental control
The indoor temperature was maintained within the range of 24-26°C, with a relative humidity level between 40% and 60%.All participants underwent exercise testing precisely 2 hours postprandial, commencing at 14:30 in the afternoon.The Tabata exercise test commenced 48 hours after the conclusion of the maximal oxygen consumption test.Subsequently, the HIIT exercise test and the MICT exercise test were conducted at 7 days intervals.

Preliminary test
Participants in this study underwent an initial maximal oxygen consumption test.The VO 2max test protocol commenced with a load intensity of 20 watts, incrementing by 15 watts every two minutes.Participants were instructed to maintain a pedaling speed of 60 revolutions per minute on the stationary bicycle.The power output corresponding to 20% VO 2max , 50% VO 2max , and 80% VO 2max intensities was determined by correlating VO 2 levels with the corresponding power output (W) achieved during the test.

Experimental procedures
Participants were sequentially and randomly assigned to undergo the Tabata test, HIIT test, and MICT test, with a 7-day interval between each session.On the day of testing, participants arrived at the laboratory at 14:30, where they engaged in a 20minute seated rest period followed by a warm-up exercise.Subsequently, they commenced the exercise test after donning the cardiopulmonary testing apparatus.Post-exercise, participants continued wearing the respiratory mask, with continuous monitoring of gas metabolism parameters during the 10-minute and 20-minute recovery periods.
The Tabata test comprised four exercises (squat, jumping jacks, high knees, burpees), each lasting 20 seconds, repeated for 2 sets.After each 20-second exercise, there was a 10-second rest, resulting in a total duration of 4 minutes.
The HIIT test involved cycling at 80% VO 2max intensity for 3 minutes, followed by cycling at 20% VO 2max intensity for 2 minutes, alternating for a total of 4 sets.Participants maintained a pedal speed of 60 revolutions per minute, and the entire session lasted 20 minutes.
For the MICT test, participants cycled at a load corresponding to 50% VO 2max intensity, maintaining a pedal speed of 60 revolutions per minute, for a continuous duration of 30 minutes.Refer to (Figure 1) for the experimental protocol.

Statistical analysis
G*power3.1.9.7, with an effect size of 0.25, an alpha value of 0.05, and a power of 0.80, was used to estimate the sample size.Based on the calculation, the minimum sample size necessary to satisfy the test requirements was 8.All data were statistically analyzed using SPSS 26.0 software (Chicago, IL, USA) and expressed as mean ± standard deviation.The Shapiro-Wilk test showed that the data were normally distributed.One way repeated measures ANOVA was used to analyze the fat oxidation rate, sugar consumption rate, energy consumption rate, fat oxidation amount, sugar oxidation amount, and energy consumption in Tabata, HIIT, and MICT groups during exercise, 10, and 20 minutes of recovery.Corrected by the Greenhouse-Geisser method when the sphericity test was violated.If significant differences were found, Bonferroni post hoc test was used to find pairwise differences.Effect sizes were reported as partial eta squared (ph 2 ) for ANOVA.(ph 2 the effect of small, medium and large were 0.04, 0.25 and 0.64.) (21) Significant differences were considered at p<0.05.

Results
Energy consumption and substrate metabolism are important indicators for evaluating exercise effectiveness.Glucose and fat are important indicators of substrate metabolism, and this study mainly monitors fat oxidation rate.Glucose oxidation rate, glucose oxidation.For energy consumption, the main monitoring is the energy expenditure rate.We monitor the energy consumption and substrate metabolism analysis data of three different exercise modes at three time points: exercise period, recovery period, exercise and the entire recovery process.The purpose is to provide theoretical basis for developing targeted training plans for overweight/obese populations from the perspectives of energy consumption and substrate metabolism.

Throughout the exercise and recovery period
Throughout the exercise and recovery period, there was a statistically significant difference in fat oxidation rates (F 2,28 = 23.416,p<0.001, ph 2 = 0.626).The overall fat oxidation rate in the Tabata group (0.27 ± 0.03g/min) was significantly higher than the HIIT group (0.20 ± 0.04g/min) (p<0.05) and the MICT group (0.20 ± 0.03g/min) (p<0.001).There was no significant difference between the HIIT group and the MICT group (p=0.854)(Figure 5A).
Throughout the exercise and recovery period, there was a statistically significant difference in overall energy expenditure (F 2,28 = 1306.546,p<0.001, ph 2 = 0.987).The overall energy expenditure in the Tabata group (91.48 ± 14.91kcal) was significantly lower than the HIIT group (248.32 ± 13.32kcal) (p<0.001) and the MICT group (252.07 ± 19.02kcal) (p<0.001).However, there was no significant difference in energy expenditure between the HIIT group and the MICT group (Figure 5F).

Heart rate and rating of perceived exertion
During the exercise period, there was a statistically significant difference in heart rate among the three exercise modes (F 2,28 = 322.533,p<0.001).In the 10-minute recovery period, there was a statistically significant difference in heart rate among the three exercise modes (F 2,28 = 102.743,p<0.001).Similarly, during the 20-minute recovery period, there was a statistically significant difference in heart rate among the three exercise modes (F 2,28 = 86.672,p<0.001) (Table 1).
Throughout the exercise period, there was a statistically significant difference RPE among the three exercise modes (F 2,28 = 147.83,p<0.001).In the 10-minute recovery period, there was a statistically significant difference in RPE among the three exercise modes (F 2,28 = 84.721,p<0.001).Additionally, during the 20-minute recovery period, there was a statistically significant difference in RPE among the three exercise modes (F 2,28 = 93.472,p<0.001) (Table 2).The findings of this study reveal that, during exercise, the MICT group exhibits a significantly higher fat oxidation quantity compared to the Tabata and HIIT groups.However, the fat oxidation rate of the MICT group only surpasses that of the HIIT group, and there is no significant difference in fat oxidation rates between the Tabata and MICT groups.The study suggests (22) that the duration of exercise significantly influences the body's ratio of glucose to lipid energy provisioning.The possible explanation lies in the relatively stable state of the body during MICT exercise at 50% VO 2max intensity.This steadiness allows the body's oxygen intake to precisely match the required oxygen quantity, gradually promoting energy conservation primarily through the utilization of fat.It is speculated that this phenomenon signifies the initiation of the body's energy-saving function.The reasons behind this may be linked to the gradual depletion of muscle glycogen, reduced glucose stores, leading to decreased levels of adrenaline and insulin, consequently enhancing the rate of fat consumption.
In terms of sugar metabolism, the HIIT group demonstrates a significantly higher glucose oxidation quantity than the Tabata and MICT groups.However, the sugar consumption rate in Tabata is notably higher than in the other two groups.Exercise intensity influences the efficiency of sugar oxidation during exercise, and as the intensity increases, so does the efficiency of sugar oxidation metabolism (23).High-intensity exercise results in rapid glycogen consumption.For instance, in 1 minute of exercise at 150% VO 2max intensity, muscle glycogen levels can decrease by 20% (24).Conversely, a set of high-intensity intermittent exercises can reduce glycogen levels to 28%-37% of pre-exercise levels (24,25).The energy consumption during exercise is significantly higher in the MICT group compared to the Tabata and HIIT groups.However, Tabata's energy consumption rate is also significantly higher than the other two groups.Moderate-intensity continuous exercise, due to its lower intensity, is easier for subjects to sustain, resulting in higher energy consumption and fat oxidation rates.This proves beneficial in preventing cardiovascular diseases, obesity, diabetes, and reducing overall mortality rates (26)(27)(28)(29).
At the same time, body composition has a significant impact on energy expenditure and substrate metabolism.Research has found that body weight has a significant impact on sugar and total energy expenditure, but has no significant effect on the proportion of fat and substrate metabolism energy supply.The reason may be that different body fat levels and body weight have a certain impact on exercise ability, with the greatest impact on defatted weight.Defatted weight is highly correlated with the aerobic and anaerobic capacity of the human body, and there is a significant difference in defatted weight between weights.Therefore, when sugar is needed for rapid oxidation energy supply, there is a significant difference in weight between weights.Gao Binghong's research found that there is a high correlation between the defatted weight, muscle weight, and anaerobic capacity of judo athletes, with a correlation coefficient between 0.66 and 0.9.It can be considered that differences in body fat levels seriously affect substrate metabolism and energy consumption.
5.2 Substrate metabolism and energy expenditure analysis during the recovery period of Tabata, HIIT, and MICT At the 10-minute recovery mark, the HIIT group exhibits a significantly higher fat oxidation rate and quantity than the MICT group, with no significant difference compared to the Tabata group.Regarding sugar metabolism, the Tabata group shows a significantly higher sugar oxidation rate and quantity than both the HIIT and MICT groups.The MICT group demonstrates significantly lower energy consumption and energy consumption rates compared to the other two groups.At the 20-minute recovery stage, the Tabata group's fat oxidation rate and quantity are significantly higher than the other two groups.In terms of sugar metabolism, there are no significant differences among the three groups.Energy consumption induced by exercise includes not only during but also post-exercise excess post-exercise energy expenditure (EPEE).This study's results indicate that while energy consumption during Tabata and HIIT exercises is significantly lower than MICT, the energy consumption during the recovery period is significantly higher than MICT.This aligns with previous research findings (30)(31)(32).With increasing exercise intensity, post-exercise sugar oxidation rates and quantities gradually decrease, while fat oxidation rates, quantities, and overall energy consumption increase.This is primarily due to the maintenance of high levels of endocrine hormones, body temperature, and pulmonary ventilation after high-intensity exercise.Oxygen reserves need rapid replenishment, the ATP-CP system requires quick supplementation, and lactate needs swift clearance.At this stage, the primary energy supply shifts from anaerobic to aerobic, with the main substance for aerobic energy supply transitioning from sugar to fat.post-exercise blood levels of free fatty acids significantly increase.Research demonstrates a correlation between the percentage of fat energy supply after exercise and exercise intensity and duration.Exercise intensity affects the amount of excess post-exercise oxygen consumption,

Funding
The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.

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FIGURE 4 Fat oxidation rate, Glucose Oxidation rate and Energy Expenditure rate of Tabata, HIIT and MICT in 20 minutes of recovery period [(A-C) n=15] Fat oxidation,Glucose Oxidation and Energy Expenditure of Tabata, HIIT and MICT in 20 minutes of recovery period [(D-F n=15] Data are expressed as mean ± SD. *p < 0.05, **p < 0.01, ***p<0.001.

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FIGURE 5 Fat oxidation rate, Glucose Oxidation rate and Energy Expenditure rate of Tabata, HIIT and MICT in the whole exercise and recovery period [(A-C) n=15] Fat oxidation,Glucose Oxidation and Energy Expenditure of Tabata, HIIT and MICT in the whole exercise and recovery period [(D-F) n=15] Data are expressed as mean ± SD. *p < 0.05, **p < 0.01, ***p<0.001.

TABLE 1
Heart rate responses over the entire trial (beats/min).