Retrospective analysis of high‐intensity focused electromagnetic procedure synchronized with radiofrequency energy for visceral fat reduction

Visceral adipose tissue (VAT), present in the abdominal cavity, oftentimes contributes to an unpleasant aesthetic appearance and can be correlated with serious health issues. High‐intensity focused electromagnetic field (HIFEM) technology with synchronized radiofrequency (RF) was recently used for abdominal body shaping through subcutaneous fat reduction and muscle growth.


| INTRODUC TI ON
Fat is a fundamental part of the human body, functioning as energy storage, insulator, protector of vital organs, co-builder of the cell wall, and initiator of many chemical reactions of basal metabolism. 1 Many types of fat tissue are recognized based on their location in the body (subcutaneous, visceral, bone marrow, and breast tissue) and function (white, brown, beige). 2 The most abundant subcutaneous adipose tissue (SAT) is found beneath the skin and serves as a metabolic sink where the excess energy intake (free fatty acid (FFA) and glycerol) is primarily stored as triglycerides (TG) in adipocytes 3 -the basic building blocks of the fat tissue. In contrast, visceral adipose tissue (VAT) occupies the abdominal cavity to protect vital organs, and besides energy storage, it acts as an endocrine and paracrine organ, influencing insulin resistance, body weight, the pathogenesis of diabetes mellitus, lipid metabolism, or inflammation. 4 The accumulation of fat is sex-specific 5 since a majority of premenopausal women tend to store the adipose tissue in the femorogluteal region resulting in a pear-shaped body contour, while a minority of women and most men tend to store the adipose tissue in the abdomen area, resulting in a displeasing apple-shaped body contour. 6 The different distribution is due to sex-specific hormones 7 and the unequal dietary fat intake between the sexes. 6 As men generally have a higher dietary intake of fat, they are expected to produce bigger lipoproteins (chylomicrons) that promote fat accumulation in the abdominal visceral area. 6 The increasing VAT amount coincides with numerous health issues, especially long-term. The visceral fat cross-sectional area (CSA) at the umbilical level exceeding 100 cm 2 is associated with elevated risks of coronary heart disease (CHD) or metabolic problems such as diabetes mellitus, further increasing the risk when the VAT area exceeds 160 cm 2 . 8 However, the amount of VAT tends to be independent of BMI, as individuals with normal BMI can also exhibit significantly increased VAT amounts and be at risk of CHD; referring to the term "metabolically obese normal weight" (MONW). 9 Fortunately, since VAT is more sensitive to lipolysis than SAT 10 (a metabolic pathway of TG hydrolysis to produce FFA and glycerol released into the bloodstream to be used by the body as an energy source 11 ), it can be maintained and even reduced by diet combined with exercise routine. 4 There are solutions for combating excessive VAT, such as bariatric surgery, for example, a roux-en-Y gastric bypass, pharmacotherapy, and exercise. 12,13 Despite the significant VAT reduction, to successfully maintain the beneficial results after surgery or pharmacotherapy, there is a demand for lifestyle changes in regards to diet and physical activity, that many cannot hold on to. 12,14 Today, proven and effective technologies in aesthetic practice may offer an alternative to such demanding lifestyle modifications. Particularly, the high-intensity focused electromagnetic field procedure (HIFEM), based on inducing supramaximal contractions, was evidenced to induce profound muscle fiber hyperplasia and hypertrophy. 15 In a retrospective analysis by Kent and Kinney, 16 the VAT-reducing effect of the HIFEM technology was firstly evidenced. Since then, a new technology combining the simultaneous application of HIFEM and synchronized radiofrequency (RF) has evolved. The addition of RF to the HIFEM energy deepens the muscle strengthening effect as it heats the muscle up to 40°C, leading to a significant increase in activation of satellite cells that regenerate and strengthen the muscle fibers. 17 This creates a more profound impact on muscle strengthening, since the results of HIFEM + RF treatments were observed to be comparable to 12-16 weeks of intensive workout. 17 Based on the previous research, 16,17 we hypothesized that the simultaneous application of HIFEM + RF technology might induce favorable changes in the VAT due to increased muscle metabolism.

| The original study population and treatment setup
This study is a retrospective analysis of a previously published prospective, multicentre, open-label, single-arm MRI study by Jacob et al. 18

| The visceral fat evaluation
The study's MRI (Matrix 380 × 380, slice thickness 5 mm, spacing 1 mm, transverse plane) data were used in this retrospective analysis.
The MRI scans were newly analyzed to evaluate the changes in VAT.
The scans in DICOM format were semi-automatically evaluated using software to reconstruct MRI images (InVesalius 3.1). The CSA corresponding to VAT was identified on two levels (L4-L5 vertebrae and L4-L5 + 5 cm, Figure 1), which closely relates to the VAT volume in the abdomen. 19 First, the threshold method was used to detect the pixels corresponding to adipose tissue automatically. Furthermore, the scans were manually checked to include only VAT in the calculations, subtracting any of the SAT-marked areas. The visceral fat CSA was then computed on both levels separately and averaged. The MRI assessment was performed by a blinded radiologist.
To determine the statistical significance of VAT change in the study, One Factor ANOVA Repeated Measures followed by Tukey HSD post-hoc test was used. The difference between the genders and measured levels was tested by two-sample Student's t-tests.
The correlation between the BMI and changes in VAT was tested by Pearson's correlation coefficient. The significance level α was set at 5% for all statistical analyses. Descriptive statistics were used to characterize the results as a mean ± SD.

| RE SULTS
In total, 16 men and 24 women (n = 40) completed the treatment visits and 1-month follow-up in the original study. A total of 29 and 20 subjects arrived for 3-month and 6-month follow-up visits, respectively, including the MRI scan visits. This drop-out was mainly attributed to the outbreak of the COVID-19 global pandemic, which restricted the patients from attending to their scheduled follow-up visits. However, one patient met the exclusion criteria, with one patient being withdrawn due to noncompliance with the protocol. The the two levels individually, the decrease was of the same magnitude in relative numbers, yet slightly but insignificantly higher at the L4-L5 + 5 cm level in absolute numbers, especially at 6 months (p > 0.05, see Table 1). There was no correlation between the BMI and the decrease in VAT during the study, r(27) = 0.21, p = 0.27, and r(18) = 0.15, p = 0.52 at 3-month and 6-month follow-up visits, respectively.

F I G U R E 1
Visualization of the levels used for retrospective evaluation of VAT using MRI scans from original study, 18 midsagittal plane.

TA B L E 1
The average decrease in VAT represented in percentage (%) and cross-sectional area (CSA, in cm 2 ) calculated from baseline; mean ± standard deviation. All differences against baseline were significant at the level of p < 0.001.

| DISCUSS ION
The main focus and objective of this retrospective study were to  VAT during the treatment. Acknowledging this limitation, we strongly encourage future prospective studies to implement other means of evaluation such as blood draws or possibly acquiring the visceral tissue specimens for detailed analysis, identifying the VAT response and corresponding patterns leading to herein proposed metabolic reduction.
Furthermore, the decrease in VAT area may not be inherently linked with an immediate impact on body health, which is likely to be propagated in the long-term. 24 Thus the benefits of VAT reduction following the non-invasive therapies should be examined further.

| CON CLUS ION
This retrospective study documented the effectiveness and safety of the HIFEM + RF procedure to reduce VAT. The results shown above demonstrate the consistency in VAT reduction regardless of sex and BMI peaking at the 3-month follow-up. The significant VAT reduction was maintained up to 6 months post-treatment. Kinney contributed to the finalization of the manuscript.

FU N D I N G I N FO R M ATI O N
This study was sponsored by BTL Industries.

CO N FLI C T O F I NTER E S T S TATEM ENT
All authors, Dr. Kent, Dr. Jacob, and Dr. Kinney are clinical investigators for BTL and do not have any potential conflicts of interest with respect to the research, authorship, and publication of this article.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available from the corresponding author upon reasonable request.

E TH I C S S TATEM ENT
The study followed the Declaration of Helsinki and all study participants signed informed consent.