Effect of Fat Mass Localization on Fat Oxidation During Endurance Exercise in Women

No sex differences in systemic metabolic responses to acute sprint interval training performed after an oral 75-g glucose load in adults with excess adiposity

BACKGROUND & AIMS

Research exploring sex-based variations in responses to acute sprint interval training (SIT) remains limited. This study aimed to examine the impact of biological sex on the systemic metabolic response to SIT. We hypothesized that acute metabolic responses to SIT would differ between males and females.

METHODS

Sedentary adults (15 males; 14 females) with excess adiposity (defined as body fat >30 %) were matched for age (32.8 ± 7.5 vs. 29.5 ± 6.5 years) and body fat mass (33.0 ± 2.9 vs. 33.2 ± 2.8 %). Following a 75-g glucose load, participants were randomly allocated to either a control (resting) or SIT trial (8 × 30 s of "all-out" cycling at a resistance of 0.075 % W kg-1 of muscle mass, interspersed with 1 min of recovery). Parameters assessed included respiratory quotient (RQ), resting energy expenditure (REE), substrate utilization rates (fat and carbohydrate), total energy output, and blood lactate and glucose levels. These were collected during fasting and at 60, 120, and 240 min post-glucose load, with the area under the curve (AUC) calculated for both trials.

RESULTS

An interaction was observed in time (P = 0.012) and trial (P < 0.001) for RQ; however, there was no significant interaction between sex × trial (P = 0.818). Males exhibited higher mean REE values than females in both conditions. Nevertheless, AUC analysis showed no significant interaction between sex and trial (P = 0.562). A significant trial × time relationship was found for fat and carbohydrate percentage contributions (P < 0.001). Post-SIT, AUCs for fat contribution (g min-1 and mg kg-1 min-1) to energy expenditure increased in both sexes compared with resting (P < 0.05), with differences noted among trials over time (P < 0.001). Blood lactate levels also increased similarly post-SIT in both sexes (P < 0.05), without a significant sex × trial interaction (AUC, P = 0.798).

CONCLUSIONS

These data demonstrate that exercise differed between the sexes and did not support the premise that acute metabolic responses to SIT would vary between males and females.

Metabolic flexibility in postmenopausal women: Hormone replacement therapy is associated with higher mitochondrial content, respiratory capacity, and lower total fat mass

AIM

To investigate effects of hormone replacement therapy in postmenopausal women on factors associated with metabolic flexibility related to whole-body parameters including fat oxidation, resting energy expenditure, body composition and plasma concentrations of fatty acids, glucose, insulin, cortisol, and lipids, and for the mitochondrial level, including mitochondrial content, respiratory capacity, efficiency, and hydrogen peroxide emission.

METHODS

22 postmenopausal women were included. 11 were undergoing estradiol and progestin treatment (HT), and 11 were matched non-treated controls (CONT). Peak oxygen consumption, maximal fat oxidation, glycated hemoglobin, body composition, and resting energy expenditure were measured. Blood samples were collected at rest and during 45 min of ergometer exercise (65% VO2peak). Muscle biopsies were obtained at rest and immediately post-exercise. Mitochondrial respiratory capacity, efficiency, and hydrogen peroxide emission in permeabilized fibers and isolated mitochondria were measured, and citrate synthase (CS) and 3-hydroxyacyl-CoA dehydrogenase (HAD) activity were assessed.

RESULTS

HT showed higher absolute mitochondrial respiratory capacity and post-exercise hydrogen peroxide emission in permeabilized fibers and higher CS and HAD activities. All respiration normalized to CS activity showed no significant group differences in permeabilized fibers or isolated mitochondria. There were no differences in resting energy expenditure, maximal, and resting fat oxidation or plasma markers. HT had significantly lower visceral and total fat mass compared to CONT.

CONCLUSION

Use of hormone therapy is associated with higher mitochondrial content and respiratory capacity and a lower visceral and total fat mass. Resting energy expenditure and fat oxidation did not differ between HT and CONT.

Influence of the different hormonal status changes during their life on fat mass localisation in women: a narrative review

CONTEXT

Independently of the total body fat mass, upper body fat mass deposition is strongly associated with cardiometabolic comorbidities. The mechanisms underlying fat mass localisation are not fully understood, but evidences indicate sex-specific fat mass distribution. Currently, data on women are scarce and the link between hormonal status changes during their life and fat mass distribution is overlooked.

METHOD

For this narrative review, literature data were extracted from the PubMed and CENTRAL databases to examine the relationship between hormonal status and adipose tissue localisation in women.

RESULTS

Menopause strongly influences fat mass localisation, while the effect of the menstrual cycle phases, oral contraception use and pregnancy has not been unambiguously determined.

CONCLUSION

Reliable data are lacking on the relationship between hormonal variations throughout the lifespan and body fat mass localisation in women. Future studies should take into account the hormonal status of women to reduce the risk of cardiometabolic diseases.

Enhanced Walking-Induced Fat Oxidation by New Zealand Blackcurrant Extract Is Body Composition-Dependent in Recreationally Active Adult Females

New Zealand blackcurrant (NZBC) extract enhanced cycling-induced fat oxidation in female endurance athletes. We examined in recreationally active females the effects of NZBC extract on physiological and metabolic responses by moderate-intensity walking and the relationship of fat oxidation changes with focus on body composition parameters. Twelve females (age: 21 ± 2 y, BMI: 23.6 ± 3.1 kg·m⁻²) volunteered. Bioelectrical bioimpedance analysis was used for body composition measurements. Resting metabolic equivalent (1-MET) was 3.31 ± 0.66 mL·kg⁻¹·min⁻¹. Participants completed an incremental walking test with oxygen uptake measurements to individualize the treadmill walking speed at 5-MET. In a randomized, double-blind, cross-over design, the 30 min morning walks were in the same phase of each participant’s menstrual cycle. No changes by NZBC extract were observed for walking-induced heart rate, minute ventilation, oxygen uptake, and carbon dioxide production. NZBC extract enhanced fat oxidation (10 responders, range: 10–66%). There was a significant correlation for changes in fat oxidation with body mass index; body fat% in legs, arms, and trunk; and a trend with fat oxidation at rest but not with body mass and habitual anthocyanin intake. The NZBC extract responsiveness of walking-induced fat oxidation is body composition-dependent and higher in young-adult females with higher body fat% in legs, arms, and trunk.

Analysis of sex-based differences in energy substrate utilization during moderate-intensity aerobic exercise

PURPOSE

To explore sex-based differences in energy substrate utilization during moderate-intensity aerobic exercise; to identify the underpinning candidate physiological mechanisms.

METHODS

Three databases were searched from inception to August 2020. Pertinent studies quantifying the utilization of substrates during moderate aerobic exercise in healthy men and reproductive-age women were considered. Studies conducted on sedentary/recreationally active and athletic populations were included and analyzed separately.

RESULTS

Thirty-five studies entered the meta-analysis (21 in sedentary/recreationally active, 14 in athletic populations). Compared to women, the respiratory exchange ratio was significantly higher both in sedentary (mean difference, MD: + 0.03; p < 0.00001) and athletic men (MD: + 0.02; p < 0.0001). Greater carbohydrate oxidation was observed both in sedentary (standardized MD, SMD: 0.53; p = 0.006) and athletic men (SMD: 1.24; p < 0.00001). Regarding lipid substrates, sedentary men oxidized less fat than women (SMD:  - 0.77; p = 0.0002), while no sex-based differences in fat oxidation were observed in athletes (SMD: 0.06; p = 0.77). Paucity of data prevented robust meta-analyses for protein sources. Sex hormones and different adrenergic activation were the most cited mechanisms to discuss sex-based differences.

CONCLUSIONS

Meta-analyses confirmed that men display greater reliance on carbohydrates while women rely more on lipids to sustain moderate aerobic exercise. The latter finding was not confirmed in athletes, a novel aspect of the present study. Mechanistically driven research is needed to further dissect the physiological underpinnings of sex differences in substrate utilization during aerobic exercise, especially for proteins, which are still less investigated than other substrates.