Ensuring optimal lipid oxidation during physical activity in overweight and obese patients using a capillary glycerol sensor.

AIM: To describe lipid oxidation during physical activity (PA) in overweight and obese patients using a real-time capillary glycerol sensor and to propose a personalized strategy to optimize lipolysis. METHODS: Healthy adult volunteers with a BMI >25 kg/m2 were recruited. All participants performed 27 sessions of 30-min PA covering all possible combinations of exercises (low, moderate, high intensities) and pre-exercise meals (high-carbohydrate, high-fat, or fasting) with 3 replicates. Glycerol measurements were performed five times during each session: at T0, T20, T30, T45, and T60. The evolution of capillary glycerolemia during PA was modeled by a nonlinear mixed-effects model. We developed a personalized PA recommendation based on the first 2 glycerolemia measurements that indicates whether a change in activity type is preferable. RESULTS: Thirteen patients were included in the study and 1232 capillary glycerolemia measurements were performed. Hyperglycemic and hyperlipidemic meals were associated with lower baseline glycerolemia (p < 0.0001 for both) compared to fasting. In contrast, the type of meal was not significantly associated with PA-induced lipolysis (p = 0.52 and p = 0.76 for high-carbohydrate and hyperlipidemic meal respectively). Compared with exercises done at low and moderate intensities, high intensity exercises were associated with a higher PA-induced lipolysis (p = 0.0002). Specific strength exercises were associated with a lower PA-induced lipolysis (p < 0.0001). The 2 initial glycerolemia measurements appeared to be a pertinent criterion which help the personalization of PA programs for such individuals (c-index 0.67). CONCLUSION: The inter-individual lipolysis responses to PA and the availability of a real-time capillary blood glycerol sensor may enable the personalization of PA programs, thus promoting optimal lipolysis in subjects with overweight and obesity.

Ultrasound-induced modifications of beef flavor characteristics during postmortem aging.

To investigate the effect of ultrasound treatment on the flavor profile of beef during postmortem aging, a comprehensive analysis of beef flavor was conducted at 0, 7, and 12 d of aging using sensory evaluation and electronic nose. Furthermore, the key volatile flavor compounds were identified using gas chromatography-mass spectrometry (GC-MS), and the odor activity value (OAV) was further evaluated. In addition, the primary pathway involved in flavor formation during beef aging after ultrasound treatment was explored. The results indicated that ultrasound enhanced the flavor profile of beef during postmortem aging by modifying the OAV of hexanal, heptanal, octanal, nonanal, decanal, (Z)-2-nonenal, dodecanal, pentanal, 1-octen-3-ol, octanoic acid, and 2-pentylfuran. Lipid oxidation was a crucial pathway through which ultrasound promoted the generation of volatile flavor compounds in beef, confirmed by the improved oxidation level of fatty acids, particularly monounsaturated ones. The study indicates that ultrasound technology can be regarded as an effective method for enhancing the beef flavor profile during postmortem aging.

Incremental supply of fat, lactose, or protein influences the diurnal pattern of heat production and substrate oxidation in pre-weaning calves.

Increasing nutrient supply to dairy calves has well known benefits; however, the effects of milk replacer (MR) composition when supplied in higher amounts are not fully understood, particularly in the first weeks of life. To better understand the metabolism of macronutrient supply in young calves (21 d old), we investigated diurnal patterns of heat production and substrate oxidation in young calves fed MR with an incremental supply of fat, lactose, or protein. Thirty-two groups of 3 mixed-sex Holstein-Friesian newborn calves (3.4 ± 1.6 d of age), were randomly assigned to one of 4 dietary treatments and studied for 21 d. Diets consisted of a basal MR (23.3% CP, 21.2% EE, and 48.8% lactose of DM) fed at 550 kJ/kg BW0.85 per day (CON; n = 24), or the basal MR incrementally supplied with 126 kJ of DE/BW0.85 per day as milk fat (+FAT; n = 23), lactose (+LAC; n = 24), or milk protein (+PRO; n = 23). Calves were fed MR in 2 daily meals and had ad libitum access to water, but were not supplied with any calf starter nor forage. After 2 weeks of adaptation to the diets, groups of 3 calves were placed for 1 week in an open-circuit respiration chamber for nitrogen and energy balance measurements (lasting 7 d). On d 3, glucose oxidation kinetics was estimated by using [U-13C]glucose. Measurements included total heat production (total energy [HP], activity [Hact] expenditure, resting metabolic rate [RMR]), respiration quotient (RQ), carbohydrate (COX) and fat oxidation (FOX) in 10 min. intervals and averaging these values per hour over days. Incremental supply of lactose and fat increased body fat deposition, with observed patterns in RMR indicating that this increase occurred primarily after the meals. Specifically, the average daily RMR was highest in the +PRO group and lowest in the CON treatment. The HP was higher in the +PRO group and throughout the day, hourly means of HP were higher in this treatment mainly caused by an increase in Hact. The recovery of 13CO2 from oral pulse-dosed [U-13C]glucose was high (77%), and not significantly different between treatments, indicating that ingested lactose was oxidized to a similar extent across treatments. Increasing lactose supply in young calves increased fat retention by reduction in fatty oxidation. Calves fed a MR with additional protein or fat raised RMR persistently throughout the day, while extra lactose supply only affects RMR after the meal. Dietary glucose was almost completely oxidized (77% based on (13C) glucose measurement) regardless of nutrient supplementation. Extra protein supply increased HP and FOX compared with similar intakes of fat and lactose. Fasting heat production (FHP) of young, group-housed calves is comparable to literature values and unaffected by energy intake. Overall, these findings deepen our understanding of how different nutrients impact metabolic processes, fat retention, and energy expenditure in young dairy calves.

Effects of post-exercise intake of exogenous lactate on energy substrate utilization at rest.

PURPOSE: This study investigated the effects of exogenous lactate intake on energy metabolism during 1 h of rest after acute exercise. METHODS: Eight-week-old ICR mice were randomly divided into four groups: SED (no treatment), EXE (exercise only), LAC (post-exercise oral lactate administration), and SAL (post-exercise saline administration) (n=8 per group). The exercise intensity was at VO2max 80% at 25 m/min and 15° slope for 50 min. After acute exercise, the LAC and SAL groups ingested lactate and saline orally, respectively, and were allowed to rest in a chamber. Energy metabolism was measured for 1 h during the resting period. RESULTS: LAC and SAL group mice ingested lactate and saline, respectively, after exercise and the blood lactate concentration was measured 1 h later through tail blood sampling. Blood lactate concentration was not significantly different between the two groups. Energy metabolism measurements under stable conditions revealed that the respiratory exchange ratio in the LAC group was significantly lower than that in the SAL group. Additionally, carbohydrate oxidation in the LAC group was significantly lower than that in the SAL group at 10-25 min. No significant difference was observed in the fat oxidation level between the two groups. CONCLUSION: We found that post-exercise lactate intake modified the respiratory exchange ratio after 1 h of rest. In addition, acute lactate ingestion inhibits carbohydrate oxidation during the post-exercise recovery period.

Exercise snacks are a time-efficient alternative to moderate-intensity continuous training for improving cardiorespiratory fitness but not maximal fat oxidation in inactive adults: a randomized controlled trial.

The aims of this study were (1) to determine how stair-climbing-based exercise snacks (ES) compared to moderate-intensity continuous training (MICT) for improving cardiorespiratory fitness (CRF), and (2) to explore whether ES could improve maximal fat oxidation rate (MFO) in inactive adults. Healthy, young, inactive adults (n: 42, age: 21.6 ± 2.3 years, BMI: 22.5 ± 3.6 kg·m-2, peak oxygen uptake (VO2peak): 33.6 ± 6.3 mL·kg-1·min-1) were randomly assigned to ES, MICT, or Control. ES (n = 14) and MICT (n = 13) groups performed three sessions per week over 6 weeks, while the control group (n = 15) maintained their habitual lifestyle. ES involved 3 × 30 s "all-out" stair-climbing (6 flight, 126 steps, and 18.9 m total height) bouts separated by >1 h rest, and MICT involved 40 min × 60%-70% HRmax stationary cycling. A significant group × time interaction was found for relative VO2peak (p < 0.05) with ES significantly increasing by 7% compared to baseline (MD = 2.5 mL·kg-1·min-1 (95% CI = 1.2, 3.7), Cohen's d = 0.44), while MICT had no significant effects (MD = 1.0 mL·kg-1·min-1 (-1.1, 3.2), Cohen's d = 0.17), and Control experienced a significant decrease (MD = -1.7 mL·kg-1·min-1 (-2.9, -0.4), Cohen's d = 0.26). MFO was unchanged among the three groups (group × time interaction, p > 0.05 for all). Stair climbing-based ES are a time-efficient alternative to MICT for improving CRF among inactive adults, but the tested ES intervention appears to have limited potential to increase MFO.

Corrigendum: Fat oxidation rates and cardiorespiratory responses during exercise in different subject populations with post-acute sequelae of SARS-CoV-2 infection: a comparison with normative percentile values.

[This corrects the article DOI: 10.3389/fphys.2023.1310319.].

Peak fat oxidation, peak oxygen uptake, and running performance increase during pre-season in sub-elite male football players.

PURPOSE: In Football, the high-intensity running bouts during matches are considered decisive. Interestingly, recent studies showed that peak fat oxidation rates (PFO) are higher in football players than other athletes. This study aimed to investigate whether PFO increases following a pre-season. Secondarily, and due to COVID-19, we investigated whether PFO is related to the physical performance in a subgroup of semi-professional male football players. METHODS: Before and after 8 weeks of pre-season training, 42 sub-elite male football players (18 semi-professionals and 24 non-professionals) had a dual-energy x-ray absorptiometry scan and performed a graded exercise test on a treadmill for the determination of PFO, the exercise intensity eliciting PFO (Fatmax) and peak oxygen uptake (V̇O2peak). Additionally, the semi-professional players performed a Yo-Yo Intermittent Recovery Test level 2 (YYIR2) before and after pre-season training to determine football-specific running performance. RESULTS: PFO increased by 11 ± 10% (mean ± 95% CI), p = 0.031, and V̇O2peak increased by 5 ± 1%, p < 0.001, whereas Fatmax was unchanged (+12 ± 9%, p = 0.057), following pre-season training. PFO increments were not associated with increments in V̇O2peak (Pearson's r2 = 0.00, p = 0.948) or fat-free mass (FFM) (r2 = 0.00, p = 0.969). Concomitantly, YYIR2 performance increased in the semi-professional players by 39 ± 17%, p < 0.001, which was associated with changes in V̇O2peak (r2 = 0.35, p = 0.034) but not PFO (r2 = 0.13, p = 0.244). CONCLUSIONS: PFO, V̇O2peak, and FFM increased following pre-season training in sub-elite football players. However, in a subgroup of semi-professional players, increments in PFO were not associated with improvements in YYIR2 performance nor with increments in V̇O2peak and FFM.

Substrate utilization and durability during prolonged intermittent exercise in elite road cyclists.

PURPOSE: This study investigated the effects of prolonged intermittent cycling exercise on peak power output (PPO) and 6-min time-trial (6 min-TT) performance in elite and professional road cyclists. Moreover, the study aimed to determine whether changes in performance in the fatigued state could be predicted from substrate utilization during exercise and laboratory measures obtained in a fresh state. METHODS: Twelve cyclists (age: 23 years [21;25]; body mass: 71.5 kg [66.7;76.8]; height: 181 cm [178;185]; V ˙ O2peak: 73.6 ml kg-1 min-1 [71.2;76.0]) completed a graded submaximal cycling test to determine lactate threshold (LT1), gross efficiency (GE), and maximal fat oxidation (MFO) as well as power output during a maximal 6 min-TT (MPO6 min) in a fresh condition. On a separate day, the cyclists completed a 4-h intermittent cycling protocol with a high CHO intake (100 g h-1). Substrate utilization and PPO was measured hourly during the protocol, which was followed by another 6 min-TT. RESULTS: MPO6 min and PPO was reduced by 10% [4;15] and 6% [0;6], respectively, after the cycling protocol. These reductions were accompanied by reductions in the anaerobic energy contribution and V ˙ O2peak, whereas the average V ˙ O2 during the 6 min-TT was unchanged. Correlation analyses showed no strong associations between reductions in MPO6 min and PPO and laboratory measures (i.e., LT1, GE, MFO, V ˙ O2peak) obtained in the fresh condition. Additionally, fat oxidation rates during the cycling protocol were not related to changes in neither PPO nor MPO6 min. CONCLUSION: PPO and MPO6 min were reduced following prolonged intermittent cycling, but the magnitude of these reductions could not be predicted from laboratory measures obtained in the fresh condition.

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.

The influence of cardiorespiratory fitness level on the relationship between work rates at the aerobic threshold (AerT) and the point of maximal fat oxidation (Fatmax) in untrained adults.

Introduction: In this study, we investigated the impact of cardiorespiratory fitness (CRF), quantified as peak oxygen consumption (VO2peak), on the relationship between work rates (WR) at the aerobic threshold (AerT) and the point of maximal fat oxidation rate (Fatmax). Methods: A total of 761 untrained adults aged 41-68 completed a one-minute incremental exercise test on a cycle ergometer, using breath-by-breath gas analysis to determine VO2peak, AerT, and Fatmax. AerT was determined using automatic and visual detection methods, and Fatmax was determined using indirect calorimetry. Participants were categorized into CRF-groups: low (<25th percentile), medium (≥25th percentile and <75th percentile), and high (≥75th percentile). Results: Fatmax was found at 43 ± 7% WRpeak, 37% ± 6% WRpeak and 35% ± 7% WRpeak in the low, medium, and high CRF-groups, respectively. In contrast, AerT was located at significantly higher relative work rates: 51% ± 8% WRpeak, 47% ± 10% WRpeak, and 47% ± 11% WRpeak in the respective CRF-groups. There was a weak agreement between Fatmax and AerT [intraclass correlation coefficient (ICC) = .19, p < .001], and the ICC decreased from .35 to .12 to .13, while the mean bias ±95% limits of agreement increased from 8% ± 14% WRpeak to 8% ± 19% WRpeak to 12% ± 44% WRpeak from CRF-low to CRF-medium to CRF-high. The mean difference between Fatmax and AerT was significantly different among the CRF subgroups: 8% ± 7% WRpeak vs. 10% ± 10% WRpeak vs. 12% ± 11% WRpeak in low, medium, and high CRF-groups, respectively. Nonetheless, multiple regression analysis revealed only a weak positive correlation between the difference in relative work rates (% WRpeak) between Fatmax and AerT (dependent variable) and the predictor variables CRF and sex, both identified as significant (R = .19, p < .001). Conclusion: Our study confirms substantial differences in exercise intensities between Fatmax and AerT in untrained adults (10% ± 19% WRpeak, ranging from -14% to 53% WRpeak). Importantly, this difference remains relatively consistent across varying CRF levels, emphasizing the distinct nature of Fatmax and AerT, with CRF playing a limited role in influencing their relationship in our study's untrained adults.

Enhancing hamburger shelf life and quality using gallic acid encapsulated in gelatin/tragacanth gum complex coacervate.

Considering mitigating oxidative degradation and inhibiting microbial proliferation in meat products, incorporating antioxidant and antimicrobial materials is critical to enhance shelf life, maintain quality, and ensure food safety. So, this study aimed to investigate the antimicrobial and antioxidant effects of encapsulated gallic acid on the quality of hamburgers during 30 days of storage. Gallic acid was microencapsulated in tragacanth gum/gelatin complex coacervate, and its encapsulation efficiency was optimized by the response surface method. The optimized encapsulation conditions were 1:4 polymer ratio (tragacanth to gelatin ratio); total polymer content, 0.9 %; pH, 3.5; and gallic acid content, 0.88 %, resulting in a 98 % encapsulation efficiency. The microcapsules were characterized using various techniques, including scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. 400 ppm encapsulated gallic acid was added to the hamburger formulation, and various microbial properties, chemical analysis (peroxide value (POV) and thiobarbituric acid (TBA)), and sensory properties of the hamburgers were evaluated during storage. Results showed that gallic acid in the hamburgers decreased lipid oxidation from 0.126 to 0.103 mg MAD/kg in the TBA test and 12.73 to 11.03 meq/kg in the POV test during one month of storage. Also, phenolic compounds could prevent the growth and proliferation of spoilage microorganisms by damaging the microorganism cell walls and changing the metabolic processes. So, the amounts of total count and yeast and mold in the treated sample were lower than in the control sample. Significantly, adding encapsulated gallic acid did not negatively affect the flavor or overall evaluation of the samples. Overall, these findings suggested that encapsulated gallic acid is a suitable candidate to maintain chemical, microbial, and sensory characteristics of hamburgers over time.

A Five-Week Periodized Carbohydrate Diet Does Not Improve Maximal Lactate Steady-State Exercise Capacity and Substrate Oxidation in Well-Trained Cyclists compared to a High-Carbohydrate Diet.

There is a growing interest in studies involving carbohydrate (CHO) manipulation and subsequent adaptations to endurance training. This study aimed to analyze whether a periodized carbohydrate feeding strategy based on a daily training session has any advantages compared to a high-carbohydrate diet in well-trained cyclists. Seventeen trained cyclists (VO2peak = 70.8 ± 6.5 mL·kg-1·min-1) were divided into two groups, a periodized (PCHO) group and a high-carbohydrate (HCHO) group. Both groups performed the same training sessions for five weeks. In the PCHO group, 13 training sessions were performed with low carbohydrate availability. In the HCHO group, all sessions were completed following previous carbohydrate intake to ensure high pre-exercise glycogen levels. In both groups, there was an increase in the maximal lactate steady state (MLSS) (PCHO: 244.1 ± 29.9 W to 253.2 ± 28.4 W; p = 0.008; HCHO: 235.8 ± 21.4 W to 246.9 ± 16.7 W; p = 0.012) but not in the time to exhaustion at MLSS intensity. Both groups increased the percentage of muscle mass (PCHO: p = 0.021; HCHO: p = 0.042) and decreased the percent body fat (PCHO: p = 0.021; HCHO: p = 0.012). We found no differences in carbohydrate or lipid oxidation, heart rate, and post-exercise lactate concentration. Periodizing the CHO intake in well-trained cyclists during a 5-week intervention did not elicit superior results to an energy intake-matched high-carbohydrate diet in any of the measured outcomes.

Impact of aerobic fitness status, menstrual cycle phase, and oral contraceptive use on exercise substrate oxidation and metabolic flexibility in females.

The influence of menstrual cycle phase and fitness status on metabolism during high-intensity interval exercise (HIIE) was assessed. Twenty-five females (24.4 (3.6) years) were categorized by normal menstrual cycle (n = 14) vs. oral contraceptive (OC) use (n = 11) and by aerobic fitness, high-fitness females (HFF; n = 13) vs. low-fitness females (LFF; n = 12). HIIE was four sets of four repetitions with a 3 min rest between intervals on a cycle ergometer at a power output halfway between the ventilatory threshold and V̇O2peak and performed during follicular (FOL: days 2-7 or inactive pills) and luteal phases (LUT: day ∼21 or 3rd week of active pills). Substrate oxidation was assessed via indirect calorimetry, blood lactate via finger stick, and recovery of skeletal muscle oxidative metabolism (mV̇O2) via continuous-wave near-infrared spectroscopy. HFF oxidized more fat (g·kg-1) during the full session (FOL: p = 0.050, LUT: p = 0.001), high intervals (FOL: p = 0.048, LUT: p = 0.001), low intervals (FOL: p = 0.032, LUT: p = 0.024), and LUT recovery (p = 0.033). Carbohydrate oxidation area under the curve was greater in HFF during FOL (FOL: p = 0.049, LUT: p = 0.124). Blood lactate was lower in LFF in FOL (p ≤ 0.05) but not in LUT. Metabolic flexibility (Δ fat oxidation g·kg-1·min-1) was greater in HFF than LFF during intervals 2-3 in FOL and 1-4 in LUT (p ≤ 0.05). Fitness status more positively influences exercise metabolic flexibility during HIIE than cycle phase or OC use.

Intense interval exercise induces greater changes in post-exercise metabolism compared to submaximal exercise in middle-aged adults.

INTRODUCTION: High-intensity interval training (HIIT) and sprint interval training (SIT) consistently elevate post-exercise metabolism compared to moderate-intensity continuous training (MICT) in young adults (18-25 years), however few studies have investigated this in middle-aged adults. PURPOSE: To assess the effect of exercise intensity on post-exercise metabolism following submaximal, near-maximal, and supramaximal exercise protocols in middle-aged adults. METHODS: 12 participants (8 females; age: 44 ± 10 years; V ˙ O2max: 35.73 ± 9.97 mL·kg-1 min-1) had their oxygen consumption ( V ˙ O2) measured during and for 2 h following 4 experimental sessions: (1) no-exercise control (CTRL); (2) MICT exercise (30 min at 65% V ˙ O2max); (3) HIIT exercise (10 × 1 min at 90% maximum heart rate with 1 min rest); and (4) modified-SIT exercise (8 × 15 s "all-out" efforts with 2 min rest). Between session differences for V ˙ O2 and fat oxidation were compared. RESULTS: O2 consumed post-exercise was elevated during the 1st h and 2nd h following HIIT (15.9 ± 2.6, 14.7 ± 2.3 L; P < 0.036, d > 0.98) and modified-SIT exercise (16.9 ± 3.3, 15.30 ± 3.4 L; P < 0.041, d > 0.96) compared to CTRL (13.3 ± 1.9, 12.0 ± 2.5 L) while modified-SIT was also elevated vs HIIT in the 1st h (P < 0.041, d > 0.96). Total post-exercise O2 consumption was elevated following all exercise sessions (MICT: 27.7 ± 4.1, HIIT: 30.6 ± 4.8, SIT: 32.2 ± 6.6 L; P < 0.027, d > 1.03) compared to CTRL (24.9 ± 4.1 L). Modified-SIT exercise increased fat oxidation (0.103 ± 0.019 g min-1) compared to all sessions post-exercise (CTRL: 0.059 ± 0.025, MICT: 0.075 ± 0.022, HIIT: 0.081 ± 0.021 g·min-1; P < 0.007, d > 1.30) and HIIT exercise increased compared to CTRL (P = 0.046, d = 0.87). CONCLUSION: Exercise intensity has an important effect on post-exercise metabolism in middle-aged adults.

A Synergistic Botanical Composition Increases Resting Energy Expenditure and Reduces Adiposity in High-Fat Diet-Fed Rats.

OBJECTIVE: An imbalance between dietary energy intake and energy expenditure may result in body fat gain or obesity. Increasing resting energy expenditure (REE) is an attractive strategy for managing body fat gain. The objective of the current study was to generate proof-of-concept data on a synergistic composition (LN19183) of Citrus aurantifolia fruit rind (CA) and Theobroma cacao seed (TC) extracts to increase REE and reduce body fat gain in a high-fat diet (HFD)-fed rats. METHOD: In in vitro cell-based experiments, CA, TC, or LN19183 were tested for fibroblast growth factor 21 (FGF-21) production from 3T3-L1 mouse adipocytes. Uncoupling protein 1 (UCP-1) and beta3-adrenergic receptor (ß3-AR) protein expressions in LN19183-treated 3T3-L1 lysates were also tested. The 56-day in vivo study in male Sprague Dawley (SD) rats (age: 12-14 weeks; body weight [b.w.]: 115-197 g) contained 2 phases of 28 days each of induction and supplementation. Seven rats received a regular rodent diet (RD) over 56 days. In the induction phase, 21 rats received HFD; in the supplementation phase, the obese rats (n = 7) received either HFD alone or in concurrence with a daily oral dose of either 100 or 250 mg/kg b.w. of LN19183 for 28 days. RESULTS: In 3T3-L1 adipocytes, LN19183 synergistically increased FGF-21 production and dose-dependently increased ß3-AR and UCP-1 protein expression. In HFD-fed rats, both doses of LN19183 supplementation significantly (p < 0.05) decreased the body weight gain, total fat mass, and liver weight and increased (p < 0.05) REE. High-dose LN19183 also significantly (p < 0.05) increased fat oxidation and UCP-1 protein expression in white fat tissue and reduced liver triglyceride (TG) level. LN19183-supplemented groups substantially reduced serum TG and glucose levels compared to the HFD rats. CONCLUSIONS: LN19183 reduces body fat mass and weight gain via increased REE and fat oxidation in HFD-fed obese rats.

Influence of the time of day in the effect of caffeine on maximal fat oxidation during exercise in women: a randomized, crossover, double-blind, and placebo-controlled study.

PURPOSE: Caffeine is a stimulant with well-recognized performance and metabolic benefits, however, there is a lack of studies investigating the time-of-day influence in the properties of caffeine to enhance fat oxidation in women. Thus, the aim of the present study was to evaluate the influence of the time of the day on the effect of caffeine on the maximal rate of fat oxidation during aerobic exercise in trained women. METHODS: Fourteen female athletes (25.5 ± 7.1 years) took part in a randomized, crossover, double-blind study. All participants undertook four different experimental trials combining the ingestion of 3 mg/kg caffeine and a placebo either in the morning (8.00-10.00 h) and in the evening (17.00-19.00 h) realizing an incremental test on a cycle ergometer with 3 min stages at workloads from 30 to 70% of maximal oxygen uptake (VO2max). Substrate oxidation rates were measured by indirect calorimetry. In each trial, the maximum rate of fat oxidation (MFO) and the intensity that elicited MFO (Fatmax) were measured. RESULTS: In comparison to placebo, MFO was significantly higher with caffeine both in the morning (0.24 ± 0.13 vs 0.30 ± 0.14 g/min; p < 0.001; ES = 0.79) and in the evening (0.21 ± 0.08 vs 0.28 ± 0.10 g/min; p = 0.002; ES = 0.72). No time-of-day effect on the capacity of caffeine to increase MFO was found (all p = 0.336) CONCLUSION: The intake of 3 mg/kg of caffeine increased the use of fat as a fuel during exercise independently of the time-of-day in trained women. TRIAL REGISTRATION: The study was registered in ClinicalTrials.gov with the following ID: NCT05880186 by 15 May 2023.

Dietary palmitic acid to oleic acid ratio modulates energy metabolism and biological rhythms in young healthy Japanese males.

The present study investigated the potential role of the composition of dietary fatty acids in the regulation of biological rhythms, such as the sleep architecture, core body temperature and leukocyte clock gene expression, in subjects fed meals rich in palmitic acid (PA) or oleic acid (OA). Eleven males participated in two sessions of indirect calorimetry in a whole-room metabolic chamber. In each session, subjects consumed three meals rich in PA (44·3 % of total fat as PA and 42·3 % as OA) or OA (11·7 % of total fat as PA and 59·3 % as OA) in the metabolic chamber. The ratio of PA to OA in plasma was significantly lower and fat oxidation was significantly higher during 24 h of indirect calorimetry in the session with meals rich in OA than in that with meals rich in PA. The duration of slow wave sleep (SWS) was shorter, the latency of SWS was longer and the nadir of core body temperature after bedtime was later in the session with meals rich in PA than in that with meals rich in OA. The peak in CRY1 gene expression was earlier and its amplitude was higher in the session with meals rich in PA than in that with meals rich in OA. In healthy young males, meals rich in PA decreased fat oxidation and disrupted biological rhythms, particularly the sleep architecture and core body temperature during sleep, more than meals rich in OA.

Intravoxel incoherent motion imaging to assess the acute effects of moderate-intensity continuous training and high-intensity interval training on thigh muscles.

This study investigated the use of intravoxel incoherent motion imaging (IVIM) to compare skeletal muscle perfusion during and after high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) to determine the impact on fat oxidation outcomes. Twenty overweight volunteers were recruited for the study. Each participant received one HIIT intervention and one MICT intervention using a cycling ergometer. Participants underwent a magnetic resonance imaging scan before, immediately after, and 1 and 2 h after each intervention. The IVIM parameters (D, fD*) of the rectus femoris, vastus lateralis, and biceps femoris long head were obtained. Changes in IVIM parameters of these muscles after both exercise interventions were compared using a two-factor repeated measures analysis of variance. In the rectus femoris, the fD* increased immediately after exercise intervention (d = 0.69 × 10-3  mm2 /s, p < 0.0083) and 2 h after exercise intervention (d = 0.64 × 10-3  mm2 /s, p < 0.0083) compared with before exercise. The increase in the fD* in the HIIT group was greater than that in the MICT group (d = 0.32, p = 0.023). In the vastus lateralis, the fD* increased immediately after the exercise intervention (d = 0.53 × 10-3  mm2 /s, p < 0.001) and returned to the pre-exercise level 1 h after exercising. The increase in the fD* in the HIIT group was lower than that in the MICT group (d = -0.21, p = 0.015). For the biceps femoris long head, the fD* was not significantly different between the two exercise interventions before and after exercise. Furthermore, the fD* 60 min after the HIIT intervention correlated with maximal oxygen consumption (VO2max), whereas fD* immediately after the MICT intervention correlated with VO2max. In summary, IVIM parameters can be used to evaluate differences in muscle perfusion between HIIT and MICT, and show a correlation with VO2max.

Association between "cluster of differentiation 36 (CD36)" and adipose tissue lipolysis during exercise training: a systematic review.

Fatty acid translocase (FAT/CD36) is a transmembrane glycoprotein belonging to the scavenger class B receptor family and is encoded by the cluster of differentiation 36 (CD36) gene. This receptor has a high affinity for fatty acids and is involved in lipid metabolism. An abundance of FAT/CD36 during exercise occurs in mitochondria and solitary muscles. As such, we aimed to systematically review the evidence for the relationship FAT/CD36 and adipose tissue lipolysis during exercise training. Five electronic databases were selected for literature searches until June 2022: PubMed, Web of Science, Scopus, science direct, and Google Scholar. We combined the different synonyms and used the operators ("AND", "OR", "NOT"): (CD36 gene) OR (CD36 polymorphism) OR (cluster of differentiation 36) OR (FAT/CD36) OR (fatty acid translocase) OR (platelet glycoprotein IV) OR (platelet glycoprotein IIIb) AND (adipose tissue lipolysis) OR (fatty acids) OR (metabolism lipid) OR (adipocytes) AND (physical effort) OR (endurance exercise) OR (high-intensity training). All published cross-sectional, cohort, case-control, and randomized clinical trials investigating CD36 polymorphisms and adipose tissue lipolysis during exercise in subjects (elite and sub-elite athletes, non-athletes, sedentary individuals and diabetics), and using valid methods to measure FAT/CD36 expression and other biomarkers, were considered for inclusion in this review. We initially identified 476 publications according to the inclusion and exclusion criteria, and included 21 studies investigating FAT/CD36 and adipose tissue lipolysis during exercise in our systematic review after examination of titles, abstracts, full texts, and quality assessments using the PEDro scale. There were nine studies with male-only participants, three with female-only participants, and nine studies included both female and male participants. There were 859 participants in the 21 selected studies. Studies were classified as either low quality (n = 3), medium quality (n = 13), and high quality (n = 5). In general, the data suggests an association between FAT/CD36 and adipose tissue lipolysis during exercise training. Improvements in FAT/CD36 were reported during or after exercise in 6 studies, while there were no changes reported in FAT/CD36 in 4 studies. An association between fat oxidation and FAT/CD36 expression during exercise was reported in 7 studies. No agreement was reached in 5 studies on FAT/CD36 content after dietary changes and physical interventions. One study reported that FAT/CD36 protein expression in muscle was higher in women than in men, another reported that training decreased FAT/CD36 protein in insulin-resistant participants, while another study reported no differences in FAT/CD36 in young, trained individuals with type 2 diabetes. Our analysis shows an association between FAT/CD36 expression and exercise. Furthermore, an association between whole-body peak fat oxidation and FAT/CD36 expression during exercise training was demonstrated. Systematic Review Registration: [PROSPERO], identifier [CRD42022342455].

Fat oxidation rates and cardiorespiratory responses during exercise in different subject populations with post-acute sequelae of SARS-CoV-2 infection: a comparison with normative percentile values.

Introduction: Post-acute sequelae of SARS-CoV-2 infection (PASC) presents a spectrum of symptoms following acute COVID-19, with exercise intolerance being a prevalent manifestation likely linked to disrupted oxygen metabolism and mitochondrial function. This study aims to assess maximal fat oxidation (MFO) and exercise intensity at MFO (FATmax) in distinct PASC subject groups and compare these findings with normative data. Methods: Eight male subjects with PASC were involved in this study. The participants were divided into two groups: "endurance-trained" subjects (V˙O2max > 55 mL/min/kg) and "recreationally active" subjects (V˙O2max < 55 mL/min/kg). Each subject performed a graded exercise test until maximal oxygen consumption (V˙O2max) to measure fat oxidation. Subsequently, MFO was assessed, and FATmax was calculated as the ratio between V˙O2 at MFO and V˙O2 max. Results: The MFO and FATmax of "endurance-trained" subjects were 0.85, 0.89, 0.71, and 0.42 and 68%, 69%, 64%, and 53%, respectively. Three out of four subjects showed both MFO and FATmax values placed over the 80th percentile of normative data. The MFO and FATmax of "recreationally active" subjects were 0.34, 0.27, 0.35, and 0.38 and 47%, 39%, 43%, and 41%, respectively. All MFO and FATmax values of those subjects placed below the 20th percentile or between the 20th and 40th percentile. Discussion: Significant differences in MFO and FATmax values between 'endurance-trained' and "recreationally active" subjects suggest that specific endurance training, rather than simply an active lifestyle, may provide protective effects against alterations in mitochondrial function during exercise in subjects with PASC.