Impact of Circadian Exercise on Metabolic Dysfunction-Associated Steatotic Liver Disease in Postmenopausal Women

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects approximately one in three adults and is a major contributor to the growing burden of cardiometabolic disease. Exercise is one of the most effective interventions for improving cardiometabolic health, reducing hepatic fat, and enhancing metabolic flexibility. However, the timing of exercise -a modifiable behavioral factor- may play a crucial yet underexplored role in determining its physiological benefits.

Preclinical studies have shown that circadian rhythms regulate key metabolic processes, including lipid metabolism and glucose homeostasis. Moreover, recent findings suggest that exercise performed at different times of day may elicit different responses, influencing the regulation of hepatic fat and systemic inflammation. These effects may be mediated, in part, through gut microbiota, which modulate host metabolism via the gut-liver axis. However, the interaction between exercise timing and gut microbiota in human physiology -particularly in women- remains poorly understood.

This knowledge gap is particularly critical in postmenopausal women, a population that experiences profound metabolic changes due to hormonal decline, including increased hepatic and visceral fat, chronic inflammation, and reduced insulin sensitivity. These alterations significantly elevate the risk for MASLD and other cardiometabolic diseases. Yet, postmenopausal women are consistently underrepresented in clinical trials exploring exercise interventions.

Based on emerging scientific evidence, the investigators hypothesize that morning exercise may lead to greater reductions in hepatic fat and improvements in cardiometabolic health compared to evening exercise in postmenopausal women with MASLD. Furthermore, the investigators propose that these effects may be partially mediated by exercise-induced changes in gut microbiota composition and function.

Thus, the main objective of the project is to investigate whether the timing of exercise modulates hepatic fat reduction, cardiometabolic adaptation, and gut microbiota remodeling in postmenopausal women with MASLD. To achieve this, the project will implement a randomized controlled trial in which 63 sedentary postmenopausal women diagnosed with MASLD will be randomly allocated into one of three groups: (i) morning exercise (07:00h), (ii) evening exercise (19:00h), or (iii) a usual-care control group receiving lifestyle recommendations.

Participants in the intervention groups will complete a 12-week supervised training program, combining aerobic and resistance exercise (3 sessions/week, 60-90 minutes per session), in accordance with WHO recommendations. Before and after the intervention, biological samples, magnetic resonance imaging, and metabolic assessments will be collected. The study will employ advanced multi-omics analyses, including metabolomics and semi-targeted metagenomics, to explore how gut microbiota changes relate to improvements in metabolism.

• Visceral adipose tissue [Time frame: Change from baseline in the mean adipose tissue content at 12 weeks]
• Intra-muscular adipose tissue [Time frame: Change from baseline in the mean adipose tissue content at 12 weeks]
• Body composition [Time frame: Change from baseline in the whole-body composition at 12 weeks]
• Bone related parameters [Time frame: Change from baseline in the whole-body mineral density and content at 12 weeks]
• Resting blood pressure [Time frame: Change from baseline in the resting blood pressure related parameters at 12 weeks]
• Glucose metabolism [Time frame: Change from baseline in the glucose related parameters at 12 weeks]
• Energy metabolism [Time frame: Change from baseline in the energy metabolism related parameters at 12 weeks]
• Cardiorespiratory Fitness [Time frame: Change from baseline in the cardiorespiratory fitness at 12 weeks]
• Muscular strength [Time frame: Change from baseline in the muscular strength related parameters at 12 weeks]
• 30 seconds sit-to-stand test [Time frame: Change from baseline in the sit-to-stand related parameters at 12 weeks]
• Heart rate and heart rate variability [Time frame: Change from baseline in the heart rate and heart rate variability related parameters at 12 weeks]
• Body weight [Time frame: Change from baseline in the body weight at 12 weeks]