Feasibility of body electrical loss analysis in detection of abdominal visceral fat

Kim Blomqvist

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

Objective: An excessive amount of abdominal visceral fat has found to be linked to metabolic and cardiovascular health much more than the body mass index (BMI). However, a cost-effective and accurate estimation of abdominal visceral fat accumulation in individuals and groups is hard. This work explores the feasibility of a novel bioimpedance-based method, named as body electrical loss analysis (BELA), aimed at estimating abdominal visceral fat that is in good agreement with estimates obtained using magnetic resonance imaging (MRI). Approach: During the BELA measurement, the subject's abdomen is covered with a radio frequency coil comprising a tunable high-Q LC resonator. No contact electrodes are attached to the subject standing within the coil. The time-varying magnetic field produced by the coil induces so-called eddy currents in the abdomen. The induced currents oppose the applied magnetic field, and from the coil's point of view power is lost, i.e., the coil is loaded. Lean body tissue that is electrically more conductive than fatty tissue loads the coil more. The loading effect is also heavily dependent on the radial distance of the tissue. So instead of just measuring the losses at some resonant frequency, the novel idea was to measure the rate of loss as a function of frequency. This was expected to have a strong relationship with the internal conductivity of the abdomen, i.e., indicating its level of adiposity. Main results: A promising correlation (r = 0.86 with SEE = 29.7 cm2) was found between the loss changing rate measured at the height of umbilicus +5 cm and the visceral fat area obtained with MRI in nine subjects recruited from laboratory personnel and acquaintances. However, the results obtained with the improved prototype in a clinical trial (17 males, 21 females, age 20–68 years, BMI 19.6–39.4 kg/m2, and waist circumference 78–128 cm) led to considerably weaker correlation, r = 0.61 with SEE = 59.30 cm2. Instead, BELA was found to correlate strongly with the circumference of abdominal wall muscles estimated from the waist circumference and the abdominal subcutaneous fat layer thickness measured with the abdominal impedance measurement (r = 0.86–0.90). The relationship with the subcutaneous fat area was found to be weak in both studies (r < 0.5), as was expected. Significance: Although the results do not suggest proposing the BELA in its current form for the prediction of abdominal visceral fat, the novelty of the method is considered a help to guide future studies on bioimpedance-based methods. The strong correlation of BELA with the circumference of abdominal wall muscles suggests its potential in other applications of body composition. The difference between the BELA and the widely used bioimpedance analysis (BIA) is that the BELA relies on the measurement of electrical loss only. No statistical gender, age, or anthropometry is used in the BELA.
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Laakso, Ilkka, Supervisor
  • Sepponen, Raimo, Advisor
Publisher
Print ISBNs978-952-60-8359-9
Electronic ISBNs978-952-60-8360-5
Publication statusPublished - 2018
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • body composition
  • abdominal visceral fat
  • electrical bioimpedance
  • BELA
  • BIA
  • MRI

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