By ADRIANA IVETTE FONSECA VERA
In general terms, aging is associated with changes in body composition with repercussions on health and physical functions. Lean components, such as body water, skeletal muscle, organ mass and bone mineral, have a tendency to diminish; while body fat rises and becomes redistributed more in the abdominal region than in other peripheral tissues (1). With this in mind, it is feasible to understand why 15 – 20% of older adults develop unintentional weight loss (more than a 5% reduction in body weight within six to 12 months), which is associated with increased morbidity and mortality (2).
In relation to this point, St-Onge and Gallagher (3) have indicated in their manuscript, published in 2010, that there is indirect evidence suggesting that the metabolic rate (MR) of individual organs is lower in older in comparison with younger individuals. Moreover, they concluded that reductions in the mass of individual organs/tissues contribute to a reduction in resting – MR that in turn generates changes in body composition favoring increased fat mass and reduced lean mass (3).
This loss of muscle mass with aging is defined as having important consequences in elderly people because it may be associated with weakness, disability, and morbidity (1). Furthermore, superimposed diseases will accelerate the loss of muscle mass, and thus enlarge the risk of disability, fragility, and death. In this context, the prevalence of sarcopenia
(progressive and generalized loss of skeletal muscle mass) increases from 13–24% among people under 70 to more than 50% among those over 80.
It is important to underline that sarcopenia has been attributed to a reduction in muscle fiber number and size, being type II fibers more susceptible than type I, to age-related fiber atrophy and loss. The extent of sarcopenia is muscle-specific, with some muscles exhibiting substantial weight reductions in elderly age, such as, for example, vastus lateralis, rectus femoris, soleus, plantaris, gastrocnemius, and extensor digitorum longus (4). However, the study conducted by Nilwik et al. (5), in 2013, has reported that reduced muscle mass with aging is mainly attributed to smaller type II fiber size and, as such, is unlikely accompanied by substantial muscle fiber loss. Therefore, increasing in muscle mass following resistance training can be linked to specific type II muscle fiber hypertrophy (5).
Another basic fact about loss of muscle mass is the association with the decline in strength in older adults, which is much more rapid than the concomitant loss of muscle mass, suggesting a decline in muscle quality. Moreover, maintaining or gaining muscle mass will not prevent aging-associated decrease in muscle strength (6). Consequently, not only physiological functions are affected, but the quality of life tends to decrease. Among the main factors that trigger weight loss in older population, it is possible to cite that some elderly individuals consume less food due to various reasons, like decreased appetite secondary to some chronic diseases, poor dentition, changes in taste/smell, food insecurity, and others. Additionally, absorption of many nutrients declines with age, creating an environment conducive to sundry nutritional deficiencies. Another major factor interfering with nutrient absorption and/or intake in elderly is the use of multiple medications (4). In the same way, bone mineral density (BMD) also declines with age, starting around 50 years of age. Recently, a triad including the simultaneous deterioration in bone, muscle and adipose tissues has been identified and named osteosarcopenic obesity syndrome; which may lead to increased risk of fractures and morbidity and decreased functionality (4).
Another variable is the change of nutritional requirements during the aging process. Due to the fact that metabolism slows, energy needs diminish but since absorption becomes less efficient, there is a higher need for nutrient-dense foods, as minerals, vitamins, protein and complex carbohydrates (4). However, although the current recommended dietary indication for protein is 0.8g/kg body weight/day for adults over the age of 19 years, several researches conducted in elderly individuals have suggested that higher quantities of protein intake (1.4–1.6 g/kg/day) would be better for older adults.
Regarding to mortality, it is stablished that involuntary weight loss is common in older persons and is a predictor of poor outcomes. A body mass index (BMI) of less than 22 has been associated with a higher mortality rate and with poorer functional status among older human beings. This higher mortality risk begins at a BMI of less than 22 in both men and women older than 65 years. At a BMI of less than 20.5 in men older than 75 years, mortality risk is 20% higher. Similarly, at a BMI of less than 18.5 in women older than 75 years, mortality risk is 40% higher (7).
In accordance with the above, Kawakamani and Hamano (8) performed a retrospective cohort study, in 2022, with the objective of elucidate about the mortality risks of body mass index in institutionalized elderly people. They included 218 elderly individuals and observed that there was a tendency to a decrease in BMI 60 months before the death of study participants; therefore, longitudinal observations of trajectories of BMI and other factors over several months to years could identify mortality risks (8).
In relation with the Body Mass Index (BMI), one of the great medical challenges is to create a separate BMI range for older people. In this context, Grzegorzewska et al. (9) performed a review of 27 literature sources, in order to analyze the accuracy of using current BMI ranges for elderly people. They concluded that the most appropriate BMI range for the elderly was 25-27 kg/m2 (except for Asian population), providing the lowest mortality, yet indicating overweight and mild obesity (9). Similar results were found in other study, which indicates that higher BMIs are associated with increased survival after age 65 years (10, 11).
Finally, as recommendation for preventing weight loss in the elderly population, it may be necessary to suggest protein supplementation (PS) and muscle strengthening exercise (MSE), due to the fact that it significantly contributes to the efficacy of the intervention in terms of muscle strength and physical activity in older patients with a higher risk of sarcopenia or frailty (12).
After this review of the literature, it is feasible to suggest in order to prevent loss of mass in elderly people:
• Maintain a healthy and balanced diet, with enough water intake, ensuring a protein intake of 1.4–1.6 g/kg/day, as well as micro and macronutrient supplementation.
• Perform resistance exercises and sports routines according to the needs and abilities of each individual, taking into account disabilities and pre-existing diseases.
• Receive specialized medical attention regarding existing comorbidities, continuing the pertinent medical check-ups and following the prescriptions received, with the aim of keeping chronic diseases as well controlled as possible.
With all above in mind, it is fair to conclude that loss of mass in elderly people is a complex process that encompasses several variables, which can interrelate with each other and conduce to a pathophysiological state of loss of lean body mass, decreased bone density and increased abdominal fat deposition. Moreover, consequences of this body change negatively affect the quality of life, as well as morbidity-mortality and the generation of frailty and disabilities. Therefore, it is essential to implement interventions for preventing it.
BIBLIOGRAPHY:
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