Journal of Exercise & Organ Cross Talk

Abstract Incretin–based therapies and protein-based dietary strategies represent two increasingly prominent approaches for fat loss in individuals with obesity, including those who engage in structured exercise. Incretin–based therapies promote weight loss primarily through appetite suppression, delayed gastric emptying, and improvements in glycemic regulation, resulting in rapid and clinically meaningful reductions in body mass. In contrast, protein-focused interventions support fat loss through enhanced satiety, preservation of diet-induced thermogenesis, and direct stimulation of muscle protein synthesis, typically producing slower but more metabolically stable changes in body composition.

For physically active individuals, the interaction between these strategies and exercise introduces additional physiological considerations beyond total weight loss. Exercise, particularly resistance training, increases the demand for adequate substrate availability to support skeletal muscle maintenance, remodeling, and functional adaptation. Importantly, these approaches also differ in the temporal pattern of fat loss, the extent to which lean mass is affected, and the durability of weight loss once active intervention slows or ceases, factors that are especially relevant for individuals pursuing long-term exercise adherence and performance.

This review synthesizes current evidence on incretin–based therapies and protein-based dietary strategies through an exercise-relevant lens, focusing on three underexamined determinants: skeletal muscle preservation, pace of fat loss, and weight-loss maintenance. Rather than positioning these approaches as competing or hierarchical, the review aims to clarify what physiological trajectories individuals may encounter when integrating each strategy with exercise. Understanding these trajectories may help practitioners and physically active individuals make more informed, context-specific decisions when selecting fat-loss interventions.

Abstract Dear Editor-in-Chief
Meteorin-like protein (METRNL) has drawn a lot of interest in the field of exercise because of its potential contribution to muscle health (Das et al., 2020). When exercising, skeletal muscle, designed for movement, goes through a variety of adaptations (Hamilton & Booth, 2000). This letter sheds light on the complex interplay between METRNL and muscle health by providing an outline of METRNL interaction with muscle tissue and the impact of exercise on this relationship.
A newly discovered adipokine called METRNL has a variety of effects on the physiology of muscles. It seems to be involved in myogenesis, muscle growth, and muscular function. According to animal research, METRNL may promote myoblast differentiation and proliferation, promoting muscle growth and repair (Lee et al., 2022). The anti-inflammatory qualities of METRNL may also lessen muscle inflammation and injury brought on by exercise.
A strong trigger for METRNL secretion is exercise. Exercise sessions, whether short-term or long-term, have been demonstrated to boost METRNL expression in circulation and muscle tissue. Numerous signaling pathways, such as those involved in metabolic adaption, muscular contraction, and inflammation, are thought to mediate this response (Alizadeh, 2021). Research is currently being done to determine the precise processes by which exercise causes the production of METRNL.
Exercise-induced METRNL release highlights its possible importance in maintaining muscular health. Exercise-related advantages like increased muscle regeneration, less inflammation, and improved energy metabolism may be aided by METRNL (Alizadeh, 2022). Exercise-induced muscular contractions and metabolic demands may trigger METRNL release, which in turn may promote additional muscle adaptation. This suggests that there may be a bidirectional relationship between exercise and METRNL.
There could be numerous clinical implications regarding fully grasping the effect of exercise on METRNL's effect on muscle health. To improve muscle regeneration, reduce muscle-related diseases, and reverse age-related muscle degeneration, strategies focused at modifying METRNL levels through exercise treatments could be investigated. To guide focused therapeutic methods, future research should concentrate on illuminating the precise connections between exercise, METRNL, and muscle health.
The connection between METRNL and muscle health is a fascinating topic of research, especially in response to exercise. Its potential as a modulator of exercise-induced muscle adaptations becomes more intriguing as our knowledge of METRNL's impact on muscle physiology expands. Exploring how exercise affects METRNL secretion and how METRNL affects muscle growth, regeneration, and function could offer fresh perspectives on how to construct exercise regimens that are most effective for different people and circumstances.