The protective effect of different polyphenols, catechin (Cat), quercetin (Qc) (flavonoids), gallic acid (GA), caffeic acid (CfA), chlorogenic acid (ChA) (phenolic acids), and capsaicin (Cap), against H₂O₂‐induced oxidative stress was evaluated in rat enterocytes using Attenuated Total Reflectance‐Fourier Transform Infrared (ATR‐FTIR) Spectroscopy and Fourier Transform Infrared Microspectroscopy (FTIRM), and results were compared to standard lipid peroxidation techniques: conjugated dienes (CD) and Thiobarbituric Acid Reactive Substances (TBARS). Analysis of ATR‐FTIR and FTIRM spectral data allowed the simultaneous evaluation of the effects of H₂O₂and polyphenols on lipid and protein oxidation. All polyphenols showed a protective effect against H₂O₂‐induced oxidative stress in enterocytes, when administered before or after H₂O₂. Cat and capsaicin showed the highest protective effect, while phenolic acids had weaker effects and Qc presented a mild prooxidative effect (IR spectral profile of biomolecules between control and H₂O₂‐treated cells) according to FTIR analyses. These results demonstrated the viability to use infrared spectroscopy to evaluate the oxidant and antioxidant effect of molecules in cell systems assays.

Exercise training performed at the maximal fat oxidation intensity (FMT) stands out as a potential treatment of overweight and obesity. This work is a meta-analysis of randomized clinical trials of studies about the effect of FMT on fat mass and maximal oxygen consumption using PubMed, SCOPUS, EBSCOhost, and ScienceDirect as databases. Two independent reviewers selected 11 trials from 356 publications identified by the following keywords: fatmax, lipoxmax, maximal fat oxidation, peak of fat oxidation, physical training, physical exercise, body fat (BF), fat mass, overweight, and obesity. The risk of bias was assessed following the Cochrane Guidelines. The pooled mean difference was computed for each outcome with the random-effects model and the inverse-variance method. The meta-analysis was performed with the RevMan software v 5.3, and the heterogeneity across studies by the I². The statistical significance was accepted at p < 0.05. Results showed that the FMT reduced body weight (MD = −4.30 kg, p < 0.01, I² = 0%), fat mass (MD = −4.03 kg, p < 0.01, I² = 0%), and waist circumference (MD = −3.34 cm, p < 0.01). Fat-free mass remains unchanged (MD = 0.08 kg, p = 0.85), but maximal oxygen consumption increased (MD = 2.96 mL∙kg⁻¹∙min⁻¹, p < 0.01, I² = 0%). We conclude that FMT at short and medium-term (eight to twenty weeks) reduces body weight and BF, increasing cardiovascular fitness in low physical fitness people with obesity.

Obesity is thought to be associated with a reduced capacity to increase fat oxidation in response to physical exercise; however, scientific evidence supporting this paradigm remains scarce. This study aimed to determine the interrelationship of different submaximal exercise metabolic flexibility (Metflex) markers and define its association with body fatness on subjects with obesity. Twenty-one male subjects with obesity performed a graded-intensity exercise protocol (Test 1) during which cardiorespiratory fitness (CRF), maximal fat oxidation (MFO) and its corresponding exercise intensity (FATmax) were recorded. A week afterward, each subject performed a 60-min walk (treadmill) at FATmax (Test 2), and the resulting fat oxidation area under the curve (TFO) and maximum respiratory exchange ratio (RER_peak) were recorded. Blood lactate (LA_b) levels was measured during both exercise protocols. Linear regression analysis was used to study the interrelationship of exercise Metflex markers. Pearson’s correlation was used to evaluate all possible linear relationships between Metflex and anthropometric measurement, controlling for CRF). The MFO explained 38% and 46% of RER_peak and TFO’s associated variance (p < 0.01) while TFO and RER_peak were inversely related (R² = 0.54, p < 0.01). Body fatness positively correlated with MFO (r = 0.64, p < 0.01) and TFO (r = 0.63, p < 0.01) but inversely related with RER_peak (r = −0.67, p < 0.01). This study shows that MFO and RER_peak are valid indicators of TFO during steady-state exercise at FATmax. The fat oxidation capacity is directly associated with body fatness in males with obesity.