Equations for Assessing Body Composition by Ultrasound in Older Adults: A Narrative Review

As individuals age, physiological changes in body composition occur, potentially contributing to adverse health outcomes in the elderly population. Various methods are used to assess body composition, but gold-standard techniques often involve technical complexity, high costs, and lack of portability. Alternative methods that are portable, relatively low-cost, and technically simpler are necessary for clinical use. Due to its portability, safety, and lower cost compared with gold-standard equipment, B-mode ultrasound has been suggested as a potential method for body composition assessment. This narrative review aimed to identify and discuss equations developed using ultrasound to assess body composition in older adults. An electronic search was conducted in the MEDLINE/PubMed, Web of Science, Scopus, and Google Scholar databases in September 2023 and updated in April 2025. The search terms used were ultrasound, body composition, muscle, fat, older adults, aging, and equation. To date, no standardized cut-off points have been established to define low muscle mass or a high body fat percentage using ultrasound in older adults. Further research is needed to determine the validity and applicability of this technique in comparison with gold standard methods, as well as among the different types of ultrasound devices (A-mode and B-mode). Caution is warranted when selecting predictive equations for assessing body composition in clinical practice in older adults, as several factors related to equipment and the population assessed must be taken into account.