Disclaimer: This blog post reflects our professional opinions based on clinical experience, patient care, and observations in practice. The perspectives shared are not derived from original clinical research and should not be interpreted as evidence-based conclusions or clinical practice guidelines. The purpose of this post is to encourage professional discussion.
Physical activity influences energy expenditure, muscle mass, functional capacity, and overall body composition. Could differences in physical activity levels contribute to an individual’s risk for malnutrition? Furthermore, should the role of physical activity in shaping body composition be taken into account when assessing for malnutrition?
How Inactivity Feeds Malnutrition
Miranda:
Physical activity, functional ability, and nutritional status are intertwined. While malnutrition is often viewed as a consequence of illness or inadequate food intake, declining activity levels reduce independence in activities of daily living (ADLs) that can both mask and accelerate the development of nutritional deficiencies. I believe that culturally, particularly here in the US, we have created an expectation that once individuals reach a certain age, such as retirement, they should slow down, sit back, and allow others to care for them. Older adults often spend more time on the sidelines rather than remaining active participants in daily life.
Although rest is important, prolonged physical inactivity can have significant mental and physical consequences that increase vulnerability to malnutrition.
A sedentary lifestyle contributes to the progressive loss of muscle and strength, reducing functional reserves over time. Initially, this decline may go unnoticed; however, when an older adult experiences a health setback such as hospitalization, surgery, or exacerbation of chronic diseases, the lack of muscle reserves becomes evident. The body has fewer protein stores to draw upon during periods of increased metabolic stress, making malnutrition more likely. This creates a cycle in which inactivity contributes to muscle loss, muscle loss reduces independence, and reduced independence further limits activity and nutritional intake.
When It's a Function Problem, Not Nutrition
Miranda:
Clinicians must distinguish between functional limitations that reduce food intake and physiological malnutrition. For instance, functional impairments such as arthritis may prevent an individual from preparing meals or feeding themselves despite having a normal appetite.
A Team-Based, Lifelong Approach
Danielle:
We can also gain clarity on these issues by leveraging the expertise of our interdisciplinary teams. Physical therapists, in particular, are experts in combating sarcopenia (age-related loss of muscle mass, strength & function), and can work with Registered Dietitians to determine the right balance of movement and nutrition. If we can shift the narrative to treat physical activity as a daily necessity rather than a chore, I’m confident we’d see a major decline in these conditions. By emphasizing these healthy aging habits early in life, starting with young and middle-aged adults, we give everyone the best chance at a fulfilling future.
Aging shouldn't carry a negative connotation; it is a privilege, and preserving our health at every stage is the most important investment we can make.
Should the Bar Move for Active Patients?
Garrett:
There is a critical need to deepen our understanding of tissue depletion levels across varying degrees of physical fitness. Current malnutrition thresholds derived from the Nutrition-Focused Physical Exam (NFPE) are largely calibrated for the general population, which we know largely fail to achieve physical activity recommendations. Consequently, baseline subcutaneous fat depletion standards likely require re-evaluation when applied to athletic or highly active populations, for example, triceps skinfold. While active individuals generally experience lower rates of hospitalization, they still face injury-related admissions or individual-specific health conditions, making them more prone to illness. In these scenarios, relying on generalized benchmarks may introduce a higher probability of inappropriate malnutrition diagnoses.
To optimize diagnostic precision, future research should investigate how distinct baseline body fat percentages and/or physical fitness influence the correlation between site-specific fat depletion and patient outcomes. Additionally, I believe it is vital to determine whether outcome-based, nutrition-related risk is driven by an absolute threshold of tissue depletion or by the percentage of muscle and/or fat mass lost relative to the patient's baseline. It is highly probable that both metrics interact, anchored by an absolute minimum physiological reserve dictated by an individual's genetics.
Ultimately, a distinct intersection exists between physical activity, physical function, and nutrition status, driven by the profound impact movement has on body composition.
