Fat Oxidation Rate Research Articles

Childhood Leukemia Survivors and Metabolic Response to Exercise: A Pilot Controlled Study.

Background: Leukemia is the most common cancer in pediatrics, with many late effects such as higher risk of dyslipidemia, insulin resistance, obesity, and metabolic syndrome. The objective of this work was to investigate substrate oxidation during submaximal exercise in survivors of childhood acute leukemia. Methods: A total of 20 leukemia survivors and 20 healthy children were matched by sex, age, and Tanner stage. They all took a submaximal incremental exercise test to determine fat and carbohydrate oxidation rates. Results: Cardiorespiratory fitness was significantly lower in leukemia survivors, with lower relative VO2 peaks (p < 0.001), lower heart rate values (p = 0.02), and lower exercise power (p = 0.012), whereas rest metabolism and body mass index did not differ between the two groups. During exercise, upward of heart rate relative to VO2 peak was significantly higher (p < 0.001) in childhood leukemia survivors. We found lower carbohydrate and fat oxidation rates (p = 0.07) in leukemia survivors compared with healthy children, and also a significantly lower relative maximal fat oxidation rate (p = 0.014). Conclusion: Despite impaired physical fitness and metabolic response to exercise, childhood leukemia survivors remained sensitive to physical activity interventions, and could readily adapt to submaximal exercise intensity.

Effects of chitosan coatings combined with resveratrol and lysozyme on the quality of Sciaenops ocellatus during refrigerated storage

AbstractThe effects of combined application of lysozyme and resveratrol with chitosan coatings on the quality of Sciaenops ocellatus during refrigerated storage were studied. Physical and chemical indices were periodically analyzed. The chitosan composite coatings were characterized, and the mechanical properties and gas permeability were also measured. The results showed that chitosan coatings could significantly reduce the total viable count (TVC), maintain tissue hardness, chewiness and sensory quality, slow the rate of fat oxidation, and restrain the increases in pH and total volatile basic nitrogen (TVB‐N). Compared with chitosan coatings, the addition of resveratrol and lysozyme had increased the tensile strength and reduced the gas permeability. The lysozyme–resveratrol–chitosan coatings had good preservation properties. The study indicated that the 0.1% lysozyme + 0.2% resveratrol + 1% chitosan group of composite coatings could maintain the quality and extend the shelf life for 8 days compared with the control group during refrigerated storage.

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

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.

Can metabolic thresholds be used as exercise intensity markers in adult men with obesity – fat burn points used as an exercise marker

We aimed to determine the exercise intensity eliciting the highest (FATmax) and the lowest (FATmin) fat oxidation rate in sedentary men with obesity and to examine if these intensities correlate with their individual aerobic (AeT) and anaerobic (AnT) thresholds, respectively. Nineteen obese males performed breath-by-breath analysis to assess maximal oxygen consumption (VO2max) and to calculate their fat oxidation rate. Pearson correlation coefficient (r), coefficient of determination (R 2) and paired t-test were used to evaluate VO2 at AeT and at FATmax and VO2 at AnT and at FATmin, respectively. FATmax and AeT occurred at 42.80±2.68% of VO2max and 43.02±2.73% of VO2max, while FATmin and AnT occurred at 53.40±3.65% of VO2max and 53.38±3.65% of VO2max, respectively. A high correlations were found between intensities matching FATmax and AeT (r=0.86, P&lt;0.01) and those at FATmin and at AnT (r=0.99, P&lt;0.01). The existing correlations suggest that metabolic thresholds may be used as exercise intensity markers assuring more tailored exercise approach in men with obesity.

The training induced increase in whole-body peak fat oxidation rate may be attenuated with aging

An attenuated ability to appropriately oxidize fat (metabolic inflexibility) has been associated with the development of obesity and type 2 diabetes. Previous studies have found that regular exercise training increases the body’s ability to oxidize fat during exercise, but also shown that fat oxidation at the same relative and absolute exercise intensity is lower in old compared with young adults. Based on these studies we investigated the effect of training status on the whole-body peak fat oxidation rate (PFO) during exercise in young and middle-aged trained and untrained men. We hypothesized that aging was associated with decreased PFO, but regular exercise training could counteract this decline. 36 healthy non-overweight young and middle-aged men were recruited into a four groups: young (27 [24–30] yrs, (Mean [95% CI])) untrained (⩒O2peak: 47 [44–49] ml/min/kg), young (28 [26–30] yrs) trained (⩒O2peak: 64 [62–67] ml/min/kg), middle-aged (55 [53–57] yrs) untrained (⩒O2peak: 37 [32–42] ml/min/kg) and middle-aged (54 [51–57] yrs) trained (⩒O2peak: 55 [51–58] ml/min/kg). PFO was measured by indirect calorimetry while subjects performed a validated incremental exercise protocol on a cycle ergometer. Whole-body peak fat oxidation rate was higher in the young trained compared to young untrained subjects (0.70 [0.65–0.75] vs.0.45 [0.36–0.54] g/min, post-hoc: p < 0.001); however, this training effect was attenuated in middle-aged trained and untrained subjects (0.44 [0.38–0.50] vs. 0.41 [0.35–0.47] g/min, post-hoc: p = 0.83, respectively). In summary, these findings suggest that the training induced effects on whole-body fat oxidation found in young men may be attenuated in middle-aged men.

Evaluating the influence of differences in methodological approach on metabolic thresholds and fat oxidation points relationship

In this study, we aimed to determine the exercise intensities eliciting the highest (FATmax) and the lowest (FATmin) fat oxidation rate in male cyclists and to compare these intensities with their individual aerobic (AeT) and anaerobic (AnT) thresholds, respectively. Twenty-two moderately trained male cyclists performed a 2-min stage graded exercise test until exhaustion using breath-by-breath gas analysis to determine maximal oxygen consumption (VO2max). The fat oxidation rate was calculated using a stoichiometric equation, with metabolic thresholds being determined by ventilatory gas analysis. In the present group of subjects, FATmax was found at a 21.34 ± 3.64 ml·kg−1·min−1 corresponding to 45.05 ± 7.68% VO2max. AeT occurred at an exercise intensity of 22.15 ± 4.84 ml·kg−1·min−1, matching 46.76 ± 10.24% VO2max. AnT and FATmin were located at intensities equivalent to 32.56 ± 5.52 ml·kg−1·min−1 and 32.30 ± 5.35 ml·kg−1·min−1 which corresponded to 68.74 ± 11.65 and 68.19 ± 11.29% VO2max, respectively. The correlation between FATmax and AeT was strong (r = 0.80, p < 0.05). No statistical difference was observed between FATmin and AnT (r = 0.99, p < 0.05). The strong relationship between observed indices can be used to provide a more tailored exercise approach.

Caffeine supplementation is ergogenic in soccer players independent of cardiorespiratory or neuromuscular fitness levels

BackgroundEquivocal findings examining the influence of caffeine on performance and biological responses to exercise may be due to inter-individual variability in cardiorespiratory or neuromuscular fitness. This study examined whether the effects of caffeine ingestion on exercise performance and biological responses to prolonged intermittent exercise to exhaustion depend on cardiorespiratory or neuromuscular fitness.MethodsTwenty male soccer players, separated according to either cardiorespiratory fitness (high vs medium) or neuromuscular fitness (high vs medium) underwent two trials simulating the cardiovascular demands of a soccer game to exhaustion on treadmill after ingesting either caffeine (6 mg∙kg− 1) or placebo. Physical performance, cardiorespiratory and metabolic parameters and blood metabolites were evaluated.ResultsTime to exhaustion (719 ± 288 vs 469 ± 228 s), jump height (42.7 ± 4.2 vs 38.6 ± 4.4 cm), heart rate (163 ± 12 vs 157 ± 13 b∙min− 1), mean arterial blood pressure (98 ± 8 vs 92 ± 10 mmHg), plasma glucose (5.6 ± 0.7 vs 5.3 ± 0.6 mmol∙l− 1) and lactate (3.3 ± 1.2 vs 2.9 ± 1.2 mmol∙l− 1) were higher, while rating of perceived exertion (12.6 ± 1.7 vs 13.3 ± 1.6) was lower with caffeine vs placebo (p < 0.01), independent of cardiorespiratory or neuromuscular fitness level. Reaction time; plasma glycerol, non-esterified fatty acids and epinephrine; carbohydrate and fat oxidation rates; and energy expenditure were not affected by caffeine (p > 0.05).ConclusionsCaffeine was effective in improving endurance and neuromuscular performance in athletes with either high or medium cardiorespiratory and neuromuscular fitness. Cardiorespiratory and neuromuscular fitness do not appear to modulate the ergogenic effects of caffeine supplementation in well-trained athletes.

Fat Oxidation Rate as a Function of Plasma Lipid and Hormone Response in Endurance Athletes.

Soria, M, Ansón, M, Lou-Bonafonte, JM, Andrés-Otero, MJ, Puente, JJ, and Escanero, J. Fat oxidation rate as a function of plasma lipid and hormone response in endurance athletes. J Strength Cond Res 34(1): 104-113, 2020-Plasma lipid changes during incremental exercise are not well known. The aim of this study was to investigate the relationship among fat oxidation rate, plasma lipids, and hormone concentrations in well-trained athletes. Twenty-six trained triathletes completed a graded cycle ergometer test to exhaustion increasing by 0.5 W·kg every 10 minutes. Fat oxidation rates were determined using indirect calorimetry. For each individual, maximal fat oxidation (MFO), the intensity at which MFO occurred (Fatmax), and the intensity at which fat oxidation became negligible (Fatmin) were determined. Blood samples for lipids and hormones analysis were collected at the end of each stage of the graded exercise test. All variables studied except insulin showed an increase at the end of incremental protocol with respect to basal levels. Free fatty acid reached significant increase at 60%VO2max and maximal levels at 70%VO2max. Low-density lipoprotein (LDL) and triglycerides (TG) decreased and showed lowest levels at 60%VO2max and reaching significant increases after 80%VO2max. High-density lipoprotein reached significant increase at 60%VO2max. Adrenaline and noradrenaline increased until the end of the incremental exercise, and significant differences were from 50%VO2max. These results suggest that exercise intensities are related to plasma lipids levels. In the zone when lipids oxidation is maximal, plasma LDL and TG variation differs from other lipids. These results may have application for the more adequate exercise intensity prescription to maximize the beneficial effects of exercise.

The influence of biological sex and fitness status on markers of recovery optimisation in response to prolonged high intensity interval exercise

This study aimed to characterise recovery outcomes and repeated performance following 2h high-intensity interval training (HIIT) exercise, followed by consumption of 1.2g/kg body mass (BM) and 0.4g/kgBM of carbohydrate and protein, respectively, between biological sex and fitness status categories. Venous blood samples, muscle biopsies, BM, body water, and breath samples were collected, and gastrointestinal symptoms (GIS) were measured, pre-exercise, and throughout 4h recovery. The following morning, participants returned to assess performance outcomes. Significantly greater body water losses were experienced by high (BM loss: 2.3%) vs. moderate fitness athletes (1.8%; P=0.009), but there were no differences between sexes (1.9%). Intestinal injury, carbohydrate malabsorption, and GIS occurred amongst all groups, with no differences. Phosphorylation of mTOR (P<0.001) and Akt (P=0.031), but not rpS6, increased from 0-2 h recovery in both fitness groups. Greater overall phosphorylation of GSK-3β was observed amongst high fitness (P=0.033). There were no group differences for glucose, insulin, cortisol, leukocyte or cytokine markers. A decline in neutrophil functional responses (36%) occurred for all groups. The following day, rates of carbohydrate oxidation were greater amongst males at all intensities. Rates of fat oxidation rates were greater at 50% and 60% VO2max, and carbohydrate oxidation were greater at 70% and 80% VO2max amongst high compared to moderate fitness athletes. Absolute performance was greater amongst high vs. moderate fitness; however, there were no differences in relative performance between groups. Recovery optimisation markers following a 2h HIIT exercise protocol and consumption of carbohydrate and protein at 1.2g/kgBM and 0.4g/kgBM, respectively, are similarly achieved by male and female athletes of moderate and high fitness status. Registration: This sub-group analysis was part of a larger study that was prospectively registered with ANZCTR (reference number 375090).

Comparison of fat oxidation rates at substrate intersection in sedentary individuals and athletes

Amaç: Bu çalışmada sporcu ve sedanter bireylerin performans testleri sonucunda tespit edilen en yüksek yağ yakım aralıkları ve substrat kesişim noktalarındaki metabolik değişkenlerin değerlendirilmesi amaçlanmıştır.Gereç ve Yöntem: Çalışmaya 10 sedanter (22,1 ± 0,5 yıl) ve 11 sporcu (22,3 ± 0,6 yıl) olmak üzere toplam 21 erkek gönüllü katılmıştır. Katılımcıların egzersiz testleri yürüme bandında indirekt kalorimetre kullanılarak yapılmıştır (Cosmed Quark CPET). Uygulanan iki farklı egzersiz testi sonucunda katılımcıların performans düzeylerine ve yağ oksidasyon hızlarına ait veriler elde edilmiştir.Bulgular: Beden kitle indekslerine göre sporcular normal, sedanter bireyler ise fazla kilolu sınıfında yer almışlar ve sedanter bireylerin vücut yüzde yağ oranları sporculara kıyasla istatistiksel olarak anlamlı düzeyde yüksek bulunmuştur. Sporcuların pik oksijen alım seviyeleri anlamlı düzeyde yüksek olmasına karşın, en yüksek yağ oksidasyon hızları sedanter bireylere benzer seviyede tespit edilmiştir. Karbonhidratların baskın enerji kaynağı haline gelmeye başladığı kesişim noktasında, sporcu ve sedanter bireylerin oksijen alım miktarları arasında istatistiksel fark olmamasına karşın, bu değerin maksimal oksijen alım kapasitelerine oranı değerlendirildiğinde sporcu grupta istatistiksel olarak anlamlı düzeyde düşük bulunmuştur. Sonuç: Oksijen alım kapasitesi yüksek olan sporcu bireylerin hem en yüksek yağ yakım hızlarının hem de kesişim noktasındaki yağ yakım hızlarının sedanter gruba kıyasla istatistiksel farklılık göstermemesi, yağ oksidasyonunu belirleyen tek faktörün maksimal aerobik kapasite olmayabileceğini düşündürmektedir.

A 28-Day Carbohydrate-Restricted Diet Improves Markers of Cardiometabolic Health and Performance in Professional Firefighters

Waldman, HS, Smith, JW, Lamberth, J, Fountain, BJ, and McAllister, MJ. A 28-day carbohydrate-restricted diet improves markers of cardiometabolic health and performance in professional firefighters. J Strength Cond Res 33(12): 3284-3294, 2019-We investigated the effects of a 4-week ad-libitum, nonketogenic, carbohydrate-restricted (<25% of calories) diet (CRD) on cardiometabolic and performance markers in firefighters (FF). Subjects (n = 15) completed 9 sessions (trials 1-3 [familiarization], trials 4-6 [baseline], and trials 7-9 [post-CRD]). Following habitual western diet, anthropometric measures were assessed, glucose tolerance measured, and then completed a graded cycling test, maximal Wingate test, and conducted their FF physical performance assessment (FPPA) to measure performance while metabolic variables and perceptual responses were recorded. Subjects then adhered to a CRD for a 4-week duration and returned for repeat testing. Body fat as measured by BodPod, and 7-site skinfold thickness decreased (p < 0.01), and a decrease was observed in blood pressure (BP) (p < 0.01; ∼5 mm Hg) after CRD. There were no differences found for glucose tolerance, but an increase was found for fat oxidation rates (p < 0.01; ∼0.07 g·min) and a decrease in carbohydrate oxidation rates across a range of intensities (p < 0.01; ∼0.24 g·min). Finally, the 2.41-km run and pull-up performance during the FPPA improved (p < 0.01; ∼41 second and 3 repetitions, respectively) and with no differences observed between treatments regarding the Wingate test. To date, this is the first CRD implemented with FF and resulted in decreased fat mass (∼2.4 kg), BP, and improvements to performance on the FPPA while preserving high-intensity exercise. These data suggest that a 28-day CRD can benefit markers of health in professional FF without detriments to occupational performance.

Acute p-synephrine ingestion increases whole-body fat oxidation during 1-h of cycling at Fatmax

p-Synephrine, the principal alkaloid of bitter orange (Citrus aurantium), is widely used in dietary supplements for weight loss due to its purported effect of increasing fat oxidation. However, there is a paucity of scientific information about its effectiveness in enhancing fat oxidation during exercise. The aim of this investigation was to determine the effect of an acute dose of p-synephrine on substrate oxidation during prolonged and constant intensity exercise. In a double-blind and randomized experiment, 14 healthy subjects performed two acute experimental trials after ingesting either p-synephrine (3mgkg-1) or a placebo (cellulose). Energy expenditure and fat oxidation rates were continuously measured by indirect calorimetry during 1h of continuous cycling at Fatmax, the intensity that induces maximal fat oxidation rate. In comparison to the placebo, energy expenditure during 1h of cycling remained unchanged with p-synephrine (698 ± 129 vs. 686 ± 123kcal, P = 0.08). However, p-synephrine increased whole-body fat oxidation (33.6 ± 10.4 vs. 37.3 ± 9.8g, P < 0.01) while also reducing carbohydrate oxidation (99.5 ± 30.4 vs. 85.0 ± 28.4g, P < 0.01). However, the magnitude of the shift on substrate oxidation induced by p-synephrine was small. Acute ingestion of p-synephrine augments fat oxidation during prolonged and constant-intensity exercise.

High fat meals increases postprandial fat oxidation rate but not postprandial lipemia

BackgroundThis study investigated the effects of ingesting meals with the same calorie intake but distinct nutritional contents after exercise on postprandial lipemia the next day.MethodsEight healthy male participants completed two 2-day trials in a random order. On day 1, the participants underwent five 12 min bouts of cycling exercise with a bout of higher intensity exercise (4 min) after each and then a bout of lower intensity cycling (2 min). The total exercise time was 90 min. After the exercise, the participants ingested three high-fat or low-fat meals. On Day 2, the participants were asked to rest in the laboratory and ingest a high-fat meal. Their postprandial reaction after a high-fat meal was observed.ResultsPostprandial triglyceride concentrations in the high-fat diet trial and low-fat diet trial exhibited nonsignificant differences. Total TG AUC were no significantly different on HF trial and LF trial (HF: 6.63 ± 3.2; LF: 7.20 ± 3.4 mmol/L*4 h. p = 0.586). However, the postprandial fat oxidation rate total AUC (HF: 0.58 ± 0.1; LF: 0.39 ± 0.2 g/min*4 h. p = 0.045), plasma glucose, and insulin concentration of the high-fat trial were significantly higher than those of the low-fat trial.ConclusionsThis study revealed that meals with distinct nutritional contents after a 90-min exercise increased the postprandial fat oxidation rate but did not influence the postprandial lipemia after a high-fat meal the next day.

Metabolic response to exercise in childhood brain tumor survivors: A pilot controlled study.

Survival rates in children diagnosed with malignant brain tumors exceed 70%. A higher risk of dyslipidemia, central obesity, and insulin resistance has been reported among these children. We investigated substrate utilization during submaximal exercise. Ten brain tumor survivors and 10 healthy children were matched by sex, age, and Tanner stage. Participants completed a submaximal incremental exercise test to determine their fat and carbohydrate oxidation rates. The relative oxygen volume (VO2 ) peak was significantly higher in the control group than in the survivors of childhood brain tumors (43.3±11.9 and 32.4±10.2mL/kg /min, P=.04). At the same relative exercise intensity, there was no difference in the carbohydrate or lipid oxidation rate between the two groups, or in the maximal fat oxidation (MFO) rate, or in the heart rate or percentage of VO2 peak to reach MFO. Healthy children achieved MFO at significantly higher muscular power than did brain tumor survivors (47.9±20.8 and 21.8±9.6 W, P=.003). Because child brain tumor survivors are less physically fit than healthy children, and substrate utilization during submaximal exercise is not different, physical activity should be promoted for child brain tumor survivors.

Controlled-release mitochondrial protonophore (CRMP) reverses dyslipidemia and hepatic steatosis in dysmetabolic nonhuman primates.

Nonalcoholic fatty liver disease (NAFLD) is estimated to affect up to one-third of the general population, and new therapies are urgently required. Our laboratory previously developed a controlled-release mitochondrial protonophore (CRMP) that is functionally liver-targeted and promotes oxidation of hepatic triglycerides. Although we previously demonstrated that CRMP safely reverses hypertriglyceridemia, fatty liver, hepatic inflammation, and fibrosis in diet-induced rodent models of obesity, there remains a critical need to assess its safety and efficacy in a model highly relevant to humans. Here, we evaluated the impact of longer-term CRMP treatment on hepatic mitochondrial oxidation and on the reversal of hypertriglyceridemia, NAFLD, and insulin resistance in high-fat, fructose-fed cynomolgus macaques (n = 6) and spontaneously obese dysmetabolic rhesus macaques (n = 12). Using positional isotopomer nuclear magnetic resonance tracer analysis (PINTA), we demonstrated that acute CRMP treatment (single dose, 5 mg/kg) increased rates of hepatic mitochondrial fat oxidation by 40%. Six weeks of CRMP treatment reduced hepatic triglycerides in both nonhuman primate models independently of changes in body weight, food intake, body temperature, or adverse reactions. CRMP treatment was also associated with a 20 to 30% reduction in fasting plasma triglycerides and low-density lipoprotein (LDL)-cholesterol in dysmetabolic nonhuman primates. Oral administration of CRMP reduced endogenous glucose production by 18%, attributable to a 20% reduction in hepatic acetyl-coenzyme A (CoA) content [as assessed by whole-body β-hydroxybutyrate (β-OHB) turnover] and pyruvate carboxylase flux. Collectively, these studies provide proof-of-concept data to support the development of liver-targeted mitochondrial uncouplers for the treatment of metabolic syndrome in humans.

Acute and sustained effects of a periodized carbohydrate intake using the sleep-low model in endurance-trained males.

Repeated periodization of carbohydrate (CHO) intake using a diet-exercise strategy called the sleep-low model can potentially induce mitochondrial biogenesis and improve endurance performance in endurance-trained individuals. However, more studies are needed to confirm the performance-related effects and to investigate the sustained effects on maximal fat oxidation (MFO) rate and proteins involved in intramuscular lipid metabolism. Thirteen endurance-trained males (age 23-44years; O2 -max, 63.9±4.6mL·kg-1 ·min-1 ) were randomized into two groups: sleep-low (LOW-CHO) or high CHO availability (HIGH-CHO) in three weekly training blocks over 4weeks. The acute metabolic response was investigated during 60minutes of exercise within the last 3weeks of the intervention. Pre- and post-intervention, 30-minute time-trial performance was investigated after a 90-minute pre-load, which as a novel approach included nine intense intervals (andestimation of MFO). Additionally, muscle biopsies (v. lateralis) were obtained to investigate expression of proteins involved in intramuscular lipid metabolism using Western blotting. During acute exercise, average fat oxidation rate was ~36% higher in LOW-CHO compared to HIGH-CHO (P=.03). This did not translate into sustained effects on MFO. Time-trial performance increased equally in both groups (overall time effect: P=.005). We observed no effect on intramuscular proteins involved in lipolysis (ATGL, G0S2, CGI-58, HSL) or fatty acid transport andβ-oxidation (CD-36 and HAD, respectively). In conclusion, the sleep-low model did not induce sustained effects on MFO, endurance performance, or proteins involved in intramuscular lipid metabolism when compared to HIGH-CHO. Our study therefore questions the transferability of acute effects of the sleep-low model to superior sustained adaptations.

Changes in substrate utilization rates during 40min of walking within the Fatmax range.

The aim of this study was to evaluate changes in fat oxidation rate during 40min of continuous exercise and identify the intensity at the highest fat oxidation rate (Fatmax). A total of 14 sedentary males with age, body height, weight, and BMI averages of 29.3 ± 0.7 years, 178.3 ± 1.7cm, 81.1 ± 3.9kg, and 25.4 ± 0.9kg/m2, respectively, were included in the study. Fatmax was determined using an indirect calorimeter with an incremental treadmill walking test at least after 12h of fasting. On a separate day, at least after 12h of fasting, the participants walked for 40min within their predetermined individual Fatmax heart rate and speed ranges. The initial fat oxidation rate was not sustained within the first 16min of exercise and was reduced; however, carbohydrate oxidation reached a stable level after nearly 10min. In sedentary individuals, during low-intensity physical activity, fat oxidation rates may not be sustainable as expected from Fatmax testing. Therefore, when exercise is prescribed, one should consider that the fat oxidation rate might decrease in sedentary overweight individuals.

Effect of high-fat diet on peripheral blood mononuclear cells and adipose tissue in early stages of diet-induced weight gain.

Subcutaneous adipose tissue (scAT) and peripheral blood mononuclear cells (PBMC) play a significant role in obesity-associated systemic low-grade inflammation. High-fat diet (HFD) is known to induce inflammatory changes in both scAT and PBMC. However, the time course of the effect of HFD on these systems is still unknown. The aim of the present study was to determine the time course of the effect of HFD on PBMC and scAT. New Zealand white rabbits were fed HFD for 5 or 10 weeks (i.e. HFD-5 and HFD-10) or regular chow (i.e. control (CNT)-5 and CNT-10). Thereafter, metabolic and inflammatory parameters of PBMC and scAT were quantified. HFD induced hyperfattyacidaemia in HFD-5 and HFD-10 groups, with the development of insulin resistance in HFD-10, while no changes were observed in scAT lipid metabolism and inflammatory status. HFD activated the inflammatory pathways in PBMC of HFD-5 group and induced modified autophagy in that of HFD-10. The rate of fat oxidation in PBMC was directly associated with the expression of inflammatory markers and tended to inversely associate with autophagosome formation markers in PBMC. HFD affected systemic substrate metabolism, and the metabolic, inflammatory and autophagy pathways in PBMC in the absence of metabolic and inflammatory changes in scAT. Dietary approaches or interventions to avert HFD-induced changes in PBMC could be essential to prevent metabolic and inflammatory complications of obesity and promote healthier living.

Diurnal Variation of Maximal Fat-Oxidation Rate in Trained Male Athletes.

To analyze the diurnal variation of maximal fat oxidation (MFO) and the intensity that elicits MFO (Fatmax) in trained male athletes. A total of 12 endurance-trained male athletes age 24.7 (4.1)y participated in the study. The authors measured MFO, Fatmax, maximum oxygen uptake (VO2max), and VO2 percentage at ventilatory threshold 2 with a graded exercise protocol performed on 2 days separated by 1 wk. One test was performed in the morning and the other in the afternoon. The authors assessed the participants' chronotype using the HÖME questionnaire. MFO and Fatmax were greater in the afternoon than in the morning (Δ = 13%, P < .001 and Δ = 6%, P = .001, respectively), whereas there were similar VO2max and ventilatory threshold 2 in the morning, than in the afternoon test (Δ = 0.2%, P = .158 and Δ = 7%, P = .650, respectively). There was a strong positive association between VO2max and MFO in both morning and afternoon assessments (R2 = .783, P = .001 and R2 = .663, P < .001, respectively). Similarly, there was a positive association between VO2max and Fatmax in both morning and afternoon assessments (R2 = .406, P = .024 and R2 = .414, P = .026, respectively). MFO and Fatmax may partially explain some of the observed diurnal variation in the performance of endurance sports.

Higher baseline fat oxidation promotes gynoid fat mobilization in response to a 12-week exercise intervention in sedentary, obese black South African women.

This 12-week exercise intervention study assessed changes in cardiorespiratory fitness (CRF), energy expenditure (EE), and substrate utilisation at rest and during exercise in obese, black South African (SA) women and explored associations with changes in body composition. Black SA women (body mass index: 30-40 kg·m-2, age: 20-35 years) were randomised into control (CTL; n = 15, maintaining usual activity) or exercise (EXE; n = 20; 12 weeks, 4 days·week-1, 40-60 min·day-1 at >70% peak heart rate) groups. Pre- and post-intervention testing included peak oxygen consumption, resting and steady state (50% peak oxygen consumption) EE, respiratory exchange, and body composition (dual-energy X-ray absorptiometry). Dietary intake (4-day) and daily step-count (ActivPAL, activPAL3c; PAL Technologies Ltd, Glasgow, UK) was collected at pre-testing and at 4, 8, and 12 weeks. EXE increased peak oxygen consumption (24.9 ± 2.4 to 27.6 ± 3.4 mL·min-1·kg-1; p < 0.001) and steady state fat oxidation rates (7.5 ± 2.5 to 9.0 ± 2.7 mg·min-1·kg-1 fat-free soft tissue mass; p = 0.003) (same relative exercise intensity). CTL remained unchanged (p > 0.05). EXE reduced proportional gynoid fat mass (percentage total fat mass, p = 0.002). Baseline resting carbohydrate oxidation rates (p = 0.036) and steady state fat oxidation rates (p = 0.021) explained 60.6% of the variability in Δgynoid fat mass (p < 0.001) in EXE. This 12-week exercise intervention improved CRF and steady state fat oxidation rates. Greater reliance on fat oxidation at baseline promoted proportional reductions in gynoid, not visceral, fat mass in response to exercise training. Novelty Combined exercise training in obese black South African women increased cardiorespiratory fitness and rates of fat oxidation during steady state exercise. Exercise training reduced proportional gynoid, not visceral, fat, potentially representing an ethnic/sex-specific response. Baseline substrate utilisation (resting and steady state exercise (50% peak oxygen uptake)) predicted changes in gynoid fat mass.