There is controversy about the relationship between ACE I/D polymorphism and health. Seventy-four healthy adults (n = 28 women; 22.5 ± 4.2 years) participated in this cross-sectional study aimed at determining the influence of ACE I/D polymorphism, ascertained by polymerase chain reaction, on cardiometabolic risk (i.e., waist circumference, body fat, blood pressure (BP), glucose, triglycerides, and inflammatory markers), maximal fat oxidation (MFO), cardiorespiratory fitness (maximal oxygen uptake), physical activity and diet. Our results showed differences by ACE I/D polymorphism in systolic BP (DD: 116.4 ± 11.8 mmHg; ID: 116.7 ± 6.3 mmHg; II: 109.4 ± 12.3 mmHg, p = 0.035) and body fat (DD: 27.3 ± 10.8%; ID: 22.6 ± 9.7%; II: 19.3 ± 7.1%, p = 0.030). Interestingly, a genotype*sex interaction in relativized MFO by lean mass (p = 0.048) was found. The DD polymorphism had higher MFO values than ID/II polymorphisms in men (8.4 ± 3.0 vs. 6.5 ± 2.9 mg/kg/min), while the ID/II polymorphisms showed higher R-MFO values than DD polymorphism in women (6.6 ± 2.3 vs. 7.6 ± 2.6 mg/kg/min). In conclusion, ACE I/D polymorphism is apparently associated with adiposity and BP, where a protective effect can be attributed to the II genotype, but not with cardiorespiratory fitness, diet and physical activity. Moreover, our study highlighted that there is a sexual dimorphism in the influence of ACE I/D gene polymorphism on MFO.

Background: Due to the prevalence and incidence worldwide of type 2 diabetes, and the significant role physical activity plays in these patients, a systematic review has been conducted to find out the effects that high-intensity interval training has on inflammatory biomarkers in subjects with type 2 diabetes. This project aims to determine the effect this training modality has on inflammatory biomarkers, in addition to observing its effects on the values of body composition and determining if this is a more effective, less effective or equally effective alternative to standard aerobic or resistance training. Methods: A search was conducted in the months of November and December 2020 on different databases: Pubmed, WoS and PEDro. A protocol for this systematic review was registered in PROSPERO (Registration number: CRD42021281186). The studies selected met the previously defined inclusion criteria, and the methodological quality of the papers used was evaluated according to the Downs and Black Checklist. Results: Out of 46 studies found, seven were included. The most relevant data concerning the characteristics of the clinical trials and HIIT characteristics, the values of body composition and the biomarkers under study were extracted from each study. Moreover, the results obtained from the different studies were described. Conclusions: HIIT could have an effect on inflammatory biomarkers. There is likely to be a relationship between changes in inflammatory profile and fat loss. A controlled diet may be a good complement to reduce the inflammatory profile. Further studies are required to determine whether HIIT is a better, worse or an equivalent alternative to medium-intensity aerobic exercise to improve the inflammatory profile.

It is unknown whether resting fat oxidation (RFO), maximal fat oxidation (MFO) and FatMax (intensity at which MFO is reached) are related to cardiometabolic risk (CMR). Thus the aim of this study was to examine the association of RFO, MFO and FatMax with CMR. 81 healthy adults (n = 31 women; 22.72 ± 4.40 years) participated in this cross‐sectional study. Glucose and triglycerides were analysed in plasma. Body composition, anthropometry, physical activity, blood pressure (BP) and heart rate measurements were taken. RFO and MFO were determined through indirect calorimetry. Maximal oxygen uptake (VO₂max) test was performed until exhaustion after MFO test. The CMR cluster was created from individual CMR factors: waist circumference, body fat percentage, systolic BP, diastolic BP, blood glucose and plasma triglycerides. Groups of high and low MFO and VO₂max were created. RFO was not associated with CMR (p < 0.05). FatMax, MFO and VO₂max were associated with individual CMR factors as waist circumference (R ² = 0.144; R ² = 0.241; R ² = 0.285; p = 0.001; respectively) and plasma triglycerides (R ² = 0.111; p = 0.004 and R ² = 0.130; p = 0.002 and R ² = 0.093; p = 0.008; respectively) and clustered CMR factors (R ² = 0.105; p = 0.008 and R ² = 0.162; p = 0.001 and R ² = 0.239; p = 0.001; respectively). VO₂max was also associated with body fat percentage (R ² = 0.105; p = 0.003) and diastolic BP (R ² = 0.083; p = 0.01), even adjusting for sex or age (p < 0.05). Groups with high level of MFO or VO₂max obtained lower CMR (p = 0.001), even adjusting for sex or age (p < 0.01). FatMax, MFO and, especially, VO₂max are associated with CMR, regardless of age and sex. However, RFO is not associated with CMR.

It is unknown how plasma leptin affects fat oxidation depending on sex in young adults. Therefore, the present cross-sectional study aimed to examine the associations of plasma leptin with resting fat oxidation (RFO), maximal fat oxidation during exercise (MFO), and insulin sensitivity, considering the different responses in men and women, and the mediating role of fatness and cardiorespiratory fitness (CRF). Sixty-five young adults (22.5 ± 4.3 years; body mass index = 25.2 ± 4.7 kg·m⁻², 23 females) participated in this study. Fasting plasma glucose, insulin, and leptin were analyzed. Variables related to insulin resistance (HOMA1-IR, HOMA2-IR), secretion (HOMA-%β), and sensitivity (HOMA-%S, QUICKI) were computed. RFO and MFO were determined through indirect calorimetry. A peak oxygen uptake (VO₂peak) test was performed until exhaustion after the MFO test. The MFO was relativized to body mass (MFO-BM) and the legs’ lean mass divided by the height squared (MFO-LI). In men, leptin was negatively associated with MFO-BM and positively with HOMA-%β (p ≤ 0.02 in both). In women, leptin was positively associated with RFO and QUICKI, and negatively with MFO-BM (p < 0.05 in all). The association between leptin and MFO was mediated by CRF (p < 0.05), but not by fat mass (p > 0.05). Plasma leptin is associated with fat oxidation and insulin secretion/sensitivity, with different responses within each sex. The association between leptin and fat oxidation is mediated by cardiorespiratory fitness.

Background: Adherence to the Mediterranean diet (MedDiet) offers multiple metabolic benefits. However, its relationship with maximal fat oxidation (MFO) and cardiorespiratory fitness (VO₂max), alongside the potential mediating role of leptin, remains underexplored in young adults. Objective: The objective was to investigate the associations between MedDiet adherence and the body mass index (BMI), MFO, and VO₂max and to evaluate whether leptin mediates these relationships. Methods: Sixty-five young adults (n = 23 women), aged 18–38, were assessed for body composition, MedDiet adherence (14-Item Mediterranean Diet Adherence Screener), MFO, and VO₂max through indirect calorimetry. Plasma leptin concentrations were measured in fasting conditions. Multiple linear regression models were performed, adjusting for sex, age, and both. Mediation analyses were conducted. Results: Higher MedDiet adherence was significantly associated with lower BMI (β = −0.339, p = 0.006) and leptin values (β = 0.284, p = 0.022) and higher absolute MFO (β = 0.338, p = 0.006) and VO₂max values (β = 0.462, p < 0.001). These associations remained significant in all models except BMI and leptin when adjusted for sex and sex and age. Leptin was positively associated with the BMI (β = 0.550, p < 0.001) and inversely associated with absolute MFO (β = −0.650, p < 0.001) in all models. There was a trend in the association between leptin and VO₂max (β = −0.233, p = 0.061) only in the unadjusted model. Mediation analysis revealed that the leptin levels significantly mediated the associations between MedDiet adherence and BMI (β = −0.358, 95% CI [−0.677, −0.077]) and VO₂max (β = 1.043, 95% CI [0.280, 1.833]). Conclusions: MedDiet adherence is associated with a lower BMI and higher MFO and VO₂max in young adults. Our findings further suggest that leptin plays a mediating role in how MedDiet adherence influences the BMI and VO₂max.