Background: It is clinically widely overlooked that many patients with Marfan syndrome (MFS) are obese, as anthropometric routine parameters are not very suitable for detection of obesity. In contrast, the Bioelectrical Impedance Analysis (BIA) provides reliable noninvasive data about the body composition of patients. The aim of the study was to assess the body composition of patients with MFS/LDS by BIA in order to detect occult obesity, which may be a risk marker for aortic or vascular complications.

Methods: In this exploratory cross-sectional study, 32 patients (56.3% female; mean age: 36.4 ± 10.7 [range: 17 - 56] years) with a molecular genetic (n=28; 87,5%) or clinical (n=4; 12,5%) diagnosis of MFS (n=28) or LDS (n=4) were enrolled between June 2020 an August 2021. All BIA-measurements were performed with the Multifrequence-Impedance-Analyzer Nutriguard-MS (Data Input, Pöcking, Germany).

Results: The MFS collective was significantly different from an age-, sex-, and Body Mass Index (BMI)-adjusted healthy control group in terms of percentage body fat (p<.001), percentage cellularity (<.001), ECM/BCM index (p<.001), and phase angle (p<.001). The mean BIA-measured bodyfat was 29.3 ± 8.2 % [range: 9.5 – 43.3%], while the mean calculated BMI of the included patients was 21.9 ± 3.6 kg/m2 [range: 15.2 – 29.7 kg/m2]. Therefore, using the obesity cut-off values for the body fat percentage of 25% in men and 35% in women, the BIA classifies as many as 14 patients (43.6%) as obese, while only 7 patients (21.9%) were pre-obese by BMI. The significant difference (p<.001) had an accordance of 40.2 %. In addition, there is a strong positive correlation (r=.480) between body fat determined by BIA and the diastolic diameter of the bulbus aortae (p=.006).

Conclusion: The fact that many patients with MFS are obese is widely unknown, although adipositas may be associated with impaired vascular endothelial function and an increased risk of cardiovascular complications. Also in patients with MFS/LDS, BIA allows a reliable assessment of the body composition beyond the normal anthropometric parameters, such as BMI. In the future, BIA-data may be of particular importance for the assessment of the vascular risk of MFS/LDS patients, besides the aortic diameters.