Does the Menstruation Cycle affect Body Composition Analysis?
Fluctuations in weight and body sensations relating to bloating and water retention are often a familiar monthly occurrence for women during the menstrual cycle. It's therefore common advice to refrain from usage of body composition analyzers that utilize Bioelectrical Impedance Analysis (BIA), due to suspicion that body water balance will be affected by the menstrual cycle, creating temporary inaccuracies.
But does the menstrual cycle actually significantly impact BIA measurements, and if so, to what extent?
A study conducted by Cumberledge and colleagues published in the International Journal of Exercise Science titled "The Effect of the Menstrual Cycle on Body Composition Determined by Contact-Electrode Bioelectrical Impedance Analyzers," directly explored this concern, investigating the influence of different phases of the menstrual cycle on body composition measurements. Their findings offer valuable insights for both individuals tracking their body composition and professionals utilizing BIA technology!
Understanding Bioelectrical Impedance Analysis
Before delving into the study's findings, it's essential to grasp the fundamental principles of BIA. This technology works by sending a low-level electrical current through the body and measuring bioelectrical impedance to this current. Different body tissues will impede the electrical current differently, and when combined with data such as height, weight, age, and gender, body composition parameters can be calculated.
While BIA offers advantages in terms of its non-invasiveness and affordability, its accuracy can be influenced by various factors, particularly hydration status. Fluctuations in body water can alter electrical conductivity and consequently affect impedance measurements, potentially leading to inaccurate estimations of fat and muscle. This is precisely why the menstrual cycle, with its known hormonal influences on fluid balance, becomes a critical area of investigation in the context of BIA.
The Study Design: Tracking Body Composition Across the Menstrual Cycle
The researchers meticulously tracked participants' menstrual cycles and conducted body composition assessments during four distinct phases:
- Menstrual Phase: The period of active menstruation.
- Follicular Phase: The phase following menstruation until ovulation.
- Early Luteal Phase: The phase after ovulation, characterized by rising progesterone levels.
- Late Luteal Phase: The phase just before the onset of menstruation, often associated with potential premenstrual symptoms, including water retention.
Throughout each menstrual cycle phase, the participants underwent body composition analysis using the four different BIA devices, thus minimizing the chances that findings would only apply to one specific device or brand.
Key Findings: Minimal Impact Across the Cycle
The most striking result of the study was the consistent lack of significant differences in body composition measurements across the four phases of the menstrual cycle, regardless of which BIA analyzer used. Statistical analysis revealed that the variations in body fat percentage, fat mass, and fat-free mass throughout the menstrual cycle were minimal and not statistically significant.
(example results from one of the devices)
This finding directly challenges the common recommendation to avoid BIA testing during perceived water retention phases of the menstrual cycle. The study's evidence suggests that at least for healthy, college-aged women, the fluctuations in fluid balance associated with the normal menstrual cycle do not substantially alter BIA body composition measurements to a degree that would compromise the reliability of the assessment.
Ostensibly, this means that BIA measurements can be reliably obtained throughout a woman's menstrual cycle without the need for specific timing considerations related to cycle phases. This simplifies the data collection process and allows for more consistent and convenient monitoring of body composition changes over time.
Is this result an anomaly?
The findings from this study align with several published papers exploring similar topics. There is one exception; a 1993 study utilizing a supine BIA device noted more significant differences for intracellular fluid, total body water, and lean body mass over the menstrual cycle. It's possible that the reason for the contrasting findings include technology (gel-based electrodes vs contact-based electrodes), measurement equations, electrical frequencies, or other unknown variables.
Potential Limitations
While this study provides valuable insights, it's important to note that the test subjects were healthy, college-aged women with regular menstrual cycles, and therefore the results might not be directly generalizable to women in other age groups, those with irregular cycles, or those with underlying health conditions that may affect fluid balance more significantly.
Conclusion
This study challenges the common recommendation to avoid testing during perceived water retention phases, and reinforces the reliability of BIA devices. While maintaining consistent testing protocols remains important, the monthly hormonal rhythm of the menstrual cycle appears to be a less significant factor influencing BIA results than previously thought.
Based on the available evidence, we suggest following the guidelines below:
- Consistency: While the menstrual cycle appears to have a minimal impact, maintaining consistent testing conditions (e.g., time of day, hydration level, food intake) is still crucial for reliable tracking of body composition changes over time.
- Focus on trends: Instead of focusing too much on on single measurements, focus instead on tracking trends in body composition over time to gain a more comprehensive understanding of changes.
- Consider Individual Variability: While the average impact of the menstrual cycle appears small, this may not necessarily be the case for every individual. Paying attention to personal sensations of fluid retention and noting the timing of measurements relative to the menstrual cycle can provide additional context.
