European Congress on Obesity (ECO2018), Vienna, Avusturya, 23 - 25 Mayıs 2018, ss.317
Phase Angle in Evaluating Nutritional Status
Deniz Güneş, B.; Acar Tek, N.; Akbulut, G.
Nutrition and Dietetics, Gazi University, Ankara/Turkey
Introduction: An accurate estimate of body composition is important in
nutrition assessment and monitoring. Bioelectrical impedance analysis
(BIA) is the most commonly used method for assessing body composition. BIA measures body component resistance (R, pure opposition of a
biological conductor to alternating electric current) and reactance (Xc,
capacitive resistance of cell membranes) by recording a voltage drop in
applied current. Resistance is related to the water content in the tissues,
while reactance is the resistive effect produced by the tissue interfaces and
cell membranes. The phase angle (PhA) is calculated directly from R and
Xc. This measure has a number of advantages, such as independence from
regression equations, and the fact that it can be calculated even in situations in which it is not possible to estimate the body composition.
Methods: Phase angle is more appropriate than impedance for the assessment of nutritional status, because PhA presents the degree of cellular
health. In healthy persons, PhA ranges from 5° to 7°. In healthy subjects,
age, sex and BMI are the major determinants of PhA. Ageing is associated
318 Obes Facts 2018;11(suppl 1):1–358 Abstracts
with decline in tissue mass, which results in decreasing PhA. Males have
higher PhA values due to higher muscle mass. Higher BMI is associated
with more cells, which increases PhA until a BMI of 30 kg/m2
. Interestingly, at BMI >40 kg/m2
, an inverse relationship with PhA is observed. This
has been attributed to increased tissue hydration or a pathological fluid
overload. Low PhA indicates pathological membrane state and function.
Low PhA may be due to over hydration and/or malnutrition. Accordingly,
many studies find a correlation between phase angle and other measures
of nutritional status and/or muscle mass.
Results: Phase angle has gained popularity over the past years since it has
shown to be highly predictive of impaired clinical outcome and mortality in a variety of diseases. PhA is frequently lower than normal in disease since influences such as infection, inflammation or disease-specific
parameters may impair phase angle. Phase angle (PhA) is a predictor of
morbidity and mortality in HIV/AIDS, pancreatic, colorectal, breast and
lung cancer, liver cirrhosis, dialysis, pulmonary disease, amyotrophic lateral sclerosis, geriatric and surgical patients. Disease-related malnutrition
is characterized by an early shift of fluids from intracellular water (ICW)
to extracellular water (ECW) space with increased ECW/ICW and a concomitant decrease in body cell mass, both lowering phase angle. In patients suffering from malnutrition, PhA can reflect the early water shift
from intracellular to extracellular space.
Conclusion: In conclusion, together with the known biological determinants, malnutrition and inflammation have a strong impact on PhA in
disease. Phase angle is a superior indicator of survival and outcome and
should therefore be used as screening tool for identification of patients at
risk because of impaired nutritional or functional status.