How BIA helps distinguish between fat loss and muscle loss in older adults

Guest writer: Rob van Berkel, Research dietitian and writer on nutrition and health

How BIA helps distinguish between fat loss and muscle loss in older adults

Unintentional loss of muscle mass and strength occurs relatively frequently in older adults. At the same time, fat mass may either increase or decrease. Both changes can negatively affect health, making it important to distinguish between muscle loss and fat loss. Bioelectrical impedance analysis (BIA) can be used for this purpose.

Unwanted Muscle Loss Is a Problem in Older Adults

Due to natural ageing, body composition changes (Palmer & Jensen, 2022). This often occurs without being directly visible in body weight. Unintentional loss of muscle mass and strength is relatively common among older adults. Natural ageing contributes to this, but inadequate nutrition (insufficient energy and protein intake), physical inactivity, and disease can exacerbate the problem (Larsson et al., 2019).

Below certain threshold values, the condition is referred to as sarcopenia, which affects approximately 10–16% of older adults worldwide (Yuan et al., 2023). Symptoms include:

  • reduced strength in the arms and/or legs;

  • difficulty rising from a chair, bed, or toilet;

  • problems climbing stairs or carrying groceries;

  • reduced walking speed and endurance;

  • quicker fatigue;

  • increased risk of falls and fractures;

  • loss of independence and possible need for long-term care.

In addition to muscle loss, (visceral) fat mass may simultaneously increase (due to inactivity) or decrease (due to illness or inadequate nutrition), which complicates the interpretation of weight changes. Distinguishing between muscle loss and fat loss is therefore essential for targeted prevention and treatment of sarcopenia and other health problems in older adults.

How Do You Measure Body Composition?

The most accurate method for measuring muscle and fat mass is DXA. However, this method is expensive and requires specialized equipment and trained personnel. Moreover, DXA uses X-rays, making it less suitable for frequent measurements.

Bioelectrical impedance analysis (BIA) is therefore a practical alternative (Cruz-Jentoft et al., 2019; Sousa-Santos et al., 2021).

BIA for Distinguishing Between Muscle Loss and Fat Loss

Bioelectrical impedance analysis (BIA) is a relatively simple, fast, and non-invasive method for measuring changes in body composition.

BIA uses a weak electrical current that passes easily through muscle tissue because it contains a high proportion of water. The current passes less easily through fat tissue, which contains little water. Based on this difference, BIA can estimate fat mass and fat-free mass (including muscle mass).

This is particularly important in older adults, where unintentional muscle loss often occurs but remains invisible on a standard scale.

When fat-free mass decreases, this indicates muscle loss, whereas a decline in fat mass indicates fat loss. Some modern BIA devices also provide segmental information per arm or leg, making it possible to detect localized muscle loss, for example in the legs.

If the device also measures phase angle, this can provide additional insight into muscle quality. A smaller phase angle indicates reduced cellular health and possible muscle breakdown (Martins et al., 2023).

In this way, BIA reveals changes that would otherwise remain hidden and helps detect unwanted muscle loss and visceral fat accumulation in older adults at an early stage.

Points of Attention for BIA Measurements

The accuracy of a BIA measurement depends on the type of device and the measurement procedure. The following considerations are important. Ensure that the client:

  • is fasted (has not eaten or drunk for 2–4 hours);

  • has not consumed caffeine or alcohol within 24 hours before measurement;

  • has an empty bladder (within 30 minutes before measurement);

  • has not exercised immediately beforehand (at least 12 hours of rest);

  • has not showered or bathed just before the measurement;

  • has not applied creams or lotions to hands or feet;

  • is measured at the same time of day each time;

  • has an adequate hydration status.

Conclusion

BIA is a practical and useful tool for distinguishing between fat loss and muscle loss in older adults. It makes changes in muscle and fat mass visible that often go unnoticed with a regular scale. By detecting muscle loss at an early stage, BIA can support the timely implementation of targeted interventions, such as resistance training or adapted nutrition, to prevent or slow sarcopenia.

Although it does not fully replace DXA, BIA offers an accessible, fast, and non-invasive method for monitoring body composition in older adults.

References

Cruz-Jentoft AJ, Bahat G, Bauer J, et al. Sarcopenia: revised European consensus on definition and diagnosis. Age Ageing. 2019;48(1):16-31.

Larsson L, Degens H, Li M, et al. Sarcopenia: Aging-Related Loss of Muscle Mass and Function. Physiol Rev. 2019;99(1):427-511.

Martins PC, Alves Junior CAS, Silva AM, Silva DAS. Phase angle and body composition: A scoping review. Clin Nutr ESPEN. 2023;56:237-250.

Palmer AK, Jensen MD. Metabolic changes in aging humans: current evidence and therapeutic strategies. J Clin Invest. 2022;132(16):e158451.

Sousa-Santos AR, Barros D, Montanha TL, Carvalho J, Amaral TF. Which is the best alternative to estimate muscle mass for sarcopenia diagnosis when DXA is unavailable?. Arch Gerontol Geriatr. 2021;97:104517.

Yuan S, Larsson SC. Epidemiology of sarcopenia: Prevalence, risk factors, and consequences. Metabolism. 2023;144:155533.

 

 

Would you like to know more about the professional body composition monitors? Then visit this page.