This study introduces a novel metabolic risk classification system that integrates body fat percentage (%BF), waist circumference (WC), and muscle strength (grip strength, GS), to provide a more comprehensive assessment of metabolic risk in young Mexican adults. Our findings underscore the importance of incorporating multiple dimensions of body composition into metabolic risk assessments, with muscle strength emerging as a critical yet often overlooked factor .
A key finding of this study is the substantial reclassification of participants when muscle strength is included in the risk assessment. Previous phenotyping systems, such as the one proposed by Gomez-Ambrosi et al. (2023), rely solely on %BF and WC, categorizing a larger proportion of individuals as "no risk” (ref. 6). However, our classification system reduces the proportion in the "no risk" category and increases those classified as increased risk. This shift suggests that conventional systems may underestimate metabolic risk, particularly in individuals with lower muscle strength, thereby missing opportunities for early intervention.
The identification of muscle strength as a critical factor in our new metabolic risk classification aligns with growing evidence that handgrip strength (HGS) serves as a reliable biomarker of overall health (ref. 13, 18–20). Just as HGS has been shown to predict various health outcomes, including cardiovascular disease and mortality, our findings suggest that integrating muscle strength into metabolic risk assessments offers a more comprehensive understanding of metabolic health (ref. 21, 22). This is particularly relevant in young adults, where traditional assessments may underestimate risk. By focusing on muscle strength, we can identify individuals at risk who might otherwise be overlooked, emphasizing the importance of early interventions aimed at enhancing muscle strength as a preventive measure against metabolic diseases (ref. 23).
This study also identifies a "protective condition" group—characterized by high muscle strength, normal %BF, and WC introducing a crucial perspective in metabolic risk assessment. The lean and strong phenotype, theoretically offering protection against cardiometabolic diseases, was notably rare in our sample, with no females and only 2.4% of males (two individuals) meeting these criteria. This rarity challenges the assumption that leanness automatically equates to health and highlights the potential risks even among those with normal %BF and WC if muscle strength is inadequate.
The absence of this protective phenotype in most participants underscores a critical public health issue: the need to move beyond conventional metrics of health that focus solely on body fat and waist circumference. Instead, our findings suggest that muscle strength should be emphasized in health interventions, especially in young adults. Strength training, which enhances insulin sensitivity and promotes the secretion of health-protective myokines like exerkines during exercise, should be prioritized in public health strategies (ref. 24–26).
This novel classification system not only exposes hidden risks among those traditionally considered low risk, but also encourages a more nuanced approach to metabolic health. By including muscle strength as a key factor, we move towards a more comprehensive understanding of metabolic well-being, promoting interventions that foster both leanness and strength as a holistic approach to preventing cardiometabolic diseases.
Despite these strengths, several limitations must be acknowledged. The cross-sectional design of our study limits the ability to establish causality or determine the directionality of the observed relationships. Future longitudinal studies are needed to determine whether low muscle strength precedes metabolic risk or is a consequence of underlying metabolic dysfunctions.
Moreover, the use of bioelectrical impedance analysis (BIA) for body composition measurement, while practical, may have limitations in accuracy, especially in individuals with extreme body compositions. Future research could benefit from using more precise methods, such as dual-energy X-ray absorptiometry (DXA), to validate these findings.
Nevertheless, this study offers a well-characterized sample and employs standardized protocols for anthropometric measurements and GS assessment. The integration of %BF, WC, and GS into a single classification system provides a more nuanced understanding of metabolic risk in young adults a group often overlooked in metabolic risk assessments.
Looking forward, there is a need to validate this new classification system in diverse populations, including different age groups, ethnicities, and physical activity levels. Understanding how this system performs across various contexts will be crucial for its broader adoption. Additionally, future research should explore the longitudinal impact of muscle strength on metabolic health outcomes. Investigating whether interventions to increase muscle strength can reduce metabolic risk and improve long-term health outcomes will be essential for establishing muscle strength as a central component of metabolic risk assessment and management.