Introduction

Obesity, characterized by excessive accumulation of body fat and associated metabolic abnormalities, is linked to a higher prevalence of chronic conditions such as diabetes mellitus, hypertension, dyslipidemia, obstructive sleep apnea, cardiovascular diseases, and certain cancers, resulting in elevated mortality rates1,2. In one previous study, it has been observed that globally, the proportion of adults with a body mass index (BMI) of 25 kg/m² or higher increased from 28.8 to 36.9% for men and from 29.8 to 38.0% for women between 1980 and 20133. This indicates a significant rise in the global obesity prevalence. Such findings underscore the seriousness of the obesity issue over time and highlight the increasing trend, further emphasizing the need for further researches in this area. The prevalence of obesity among adults in Korea is 36.3% as of 2019, with a consistent upward trend over the past decade4.

Abdominal obesity, defined by excessive fat accumulation in the abdominal region, particularly correlates with increased risk of cardiovascular diseases5. Assessment of abdominal obesity typically involves measuring waist circumference, with criteria defining abdominal obesity as waist circumferences ≥ 90 cm for men and ≥ 85 cm for women in Korean populations6. Imaging techniques like computed tomography (CT) can accurately assess visceral fat accumulation, a key predictor of metabolic syndrome7. Abdominal obesity contributes to insulin resistance, impaired fasting glucose, dyslipidemia, and hypertension, underscoring its significance as a precursor to metabolic syndrome8,9. Therefore, body shape correction, especially through the management of abdominal obesity, can be considered an important medical practice. Surgical interventions for body contouring, while effective, may entail complications such as pain, swelling, scarring, and infection. Consequently, non-invasive body contouring devices have gained popularity for their ability to address aesthetic concerns without surgical risks10. However, evidence supporting the combined use of ultrasound-based body contouring and radiofrequency-based skin tightening techniques for abdominal obesity management in Koreans remains limited.

Thus, this study aims to evaluate the effectiveness of combining these techniques in reducing abdominal circumference and subcutaneous fat volume, thereby addressing abdominal obesity among Korean women.

Materials and methods

Data source and study subjects

This study retrospectively analyzed clinical data obtained during treatment processes that had already been completed at Ewha Womans University Seoul Hospital. The study included women aged 18 years or older who visited the Well Aging Center at Ewha Womans University Seoul Hospital between January 1, 2023, and December 31, 2023.

Inclusion criteria were as follows:

  1. 1.

    Patients who underwent ultrasound-based body contouring using the UltraSpeed™ handpiece (Alma Accent Prime™ platform) and radiofrequency-based skin tightening using the UniForm™ handpiece (Alma Accent Prime™ platform).

  2. 2.

    Patients whose waist circumference was measured both before and after the procedure.

  3. 3.

    Patients who underwent abdominal fat computed tomography (CT) scans to assess subcutaneous and visceral fat areas.

Exclusion criteria included individuals with incomplete data required for analysis or those who died during the study period.

The UltraSpeed™ handpiece utilizes non-focused ultrasound technology delivered through a large plate-type sonotrode that generates acoustic-guided vibration waves to disrupt subcutaneous adipose tissue, facilitating body contouring. The UniForm™ handpiece employs radiofrequency energy to improve skin elasticity and stimulate collagen remodeling by generating heat in the dermal layers.

To minimize risks to participants, no prospective data collection for research purposes was conducted. All information was fully de-identified by removing personal identifiers and replacing them with unique identification codes. As such, the risk to participants did not exceed minimal risk. A waiver of informed consent was approved by the Institutional Bioethics Committee of Ewha Womans University Seoul Hospital (IRB approval number: SEUMC 2024-03-029).

Ethical approval

All methods in this study were carried out in accordance with relevant guidelines and regulations. The study protocol was reviewed and approved by the Institutional Bioethics Committee of Ewha Womans University Seoul Hospital (IRB file number: SEUMC 2024-03-029). As this study involved retrospective analysis of de-identified clinical data, obtaining informed consent from participants was waived by the ethics committee.

Analytical approach and statistics

Continuous variables were expressed as mean ± standard deviation (SD) or median (interquartile range, IQR), as appropriate. Pre- and post-treatment measurements were compared using the non-parametric Wilcoxon signed-rank test to evaluate changes in waist circumference, maximum waist circumference, subcutaneous fat area, visceral fat area, and total fat area at the umbilicus level among subjects who received abdominal treatment. This statistical method was chosen due to the small sample size (n = 9) and the non-normal distribution of the data. Statistical analyses were conducted using IBM SPSS Statistics version 29.0.2.0 (IBM Co., Armonk, NY, USA). A two-sided p-value of less than 0.05 was considered statistically significant.

Additionally, no missing data were encountered in this study, and all analyses were conducted on complete datasets. The time interval (in days) between the ultrasound-based body contouring session and the radiofrequency-based skin tightening session was also recorded for each participant. This information is presented in Table 1 to provide a detailed understanding of the treatment timeline.

Results

In this study, a total of 9 women participants underwent combined ultrasound-based body contouring and radiofrequency-based skin tightening techniques. The results demonstrated significant changes in several key metrics of abdominal obesity (Table 1). Table 1 summarizes the detailed data for each subject, including waist circumference, fat area measurements before and after treatment, and the time interval (in days) between the ultrasound-based body contouring and radiofrequency-based skin tightening sessions.

The mean reduction in waist circumference (ΔWC) was − 3.83 cm (SD = 1.79, p < 0.01). This consistent reduction across participants, ranging from − 1.00 cm to -6.50 cm, indicates a significant decrease in abdominal girth post-treatment. The average reduction in maximum waist circumference (ΔWC Max) was − 3.91 cm (SD = 2.52, p < 0.01). These reductions varied from − 1.00 cm to -7.70 cm, suggesting the treatment’s efficacy in addressing not just the baseline but also the maximal abdominal expansion. The treatments resulted in a mean decrease of 18.90 cm² in the superficial fat area (SFA) (SD = 13.70, p < 0.01). This significant reduction highlights the ability of the combined techniques to effectively reduce superficial abdominal fat. Contrary to other measurements, the visceral fat area (VFA) did not exhibit a statistically significant change (mean ΔVFA = -1.48 cm², SD = 10.63, p > 0.05). This suggests that the procedures predominantly target superficial layers of fat rather than deeper visceral fat. The total fat area(TFA) showed a significant mean reduction of 20.38 cm² (SD = 15.87, p < 0.01), indicating an overall decrease in abdominal fat content post-treatment.

Table 2 provides a summary of these changes and their statistical significance. The data illustrates that while significant reductions were observed in most metrics, the lack of change in visceral fat underscores the need for additional research to understand the differential effects of the treatments on various fat compartments.

Relative percentage changes were calculated for waist circumference (ΔWC %), maximum waist circumference (ΔWC Max%), superficial fat area (ΔSFA %), visceral fat area (ΔVFA %), and total fat area (ΔTFA %) to provide a standardized metric for evaluating treatment effects across participants. These calculations were performed using the formula:

\(\Delta \% =\frac{{Post\,treatment\,value - \Pr e\,\,treatment\,value}}{{\Pr e\,\,treatment\,value}} \times 100\)

The relative percentage changes have been included in Table 3 to enhance the interpretability of the results. Relative percentage changes revealed a similar trend, with significant reductions observed in waist circumference (△WC%)( -4.35%, p < 0.01), maximum waist circumference (△WC_Max%)( -4.14%, p < 0.01), superficial fat area (△SFA%)(-7.19%, p < 0.01), and total fat area (△TFA%)( -5.67%, p < 0.01). Visceral fat area (△VFA%) (-1.46%) did not show significant changes (p > 0.05).

These findings highlight the efficacy of the applied techniques in targeting superficial fat, as corroborated by Table 3. The consistency between absolute and relative percentage reductions highlights the robustness of the treatment effects across different metrics and further supports the efficacy of these non-invasive methods in managing abdominal obesity among Korean women.

Table 1 Detailed subject data before and after intervention.
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Table 2 Summary statistics and p-values for body composition changes.
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Table 3 Relative percentage changes and P-values for body composition.
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Discussion

This study investigated the effectiveness of combining ultrasound-based body contouring and radiofrequency-based skin tightening techniques on abdominal obesity in Korean women. These non-invasive procedures aimed to reduce abdominal circumference and subcutaneous fat volume. The results demonstrated statistically significant changes in waist circumference, maximum waist circumference, superficial fat area, and total fat area after the treatments. Visceral fat area did not show a statistically significant difference.

Patients often experience initial reductions in visceral fat during weight loss, while reductions in subcutaneous fat take longer, leading to frustration for some individuals. In this context, the findings of this study confirm that ultrasound-based body contouring and radiofrequency-based skin tightening techniques can be effective for reducing abdominal circumference and subcutaneous fat volume in female patients.

The thermal disruption of adipose tissue by ultrasound and radiofrequency technologies involves several mechanisms. Ultrasound induces mechanical vibrations that disrupt adipocyte membranes, leading to triglyceride release and subsequent cellular apoptosis or necrosis11,12. Radiofrequency generates heat through electromagnetic waves, which accelerates adipocyte metabolism via lipase-mediated triglyceride degradation and promotes apoptosis13. Additionally, both modalities improve local blood circulation by inducing vasodilation, enhancing oxygen supply, and stimulating fibroblast activity for collagen remodeling14. These combined effects contribute to reductions in subcutaneous fat volume and improvements in skin elasticity.

The relative percentage results align with these findings, as superficial fat was most affected by the interventions with a mean reduction of 7.19%. This supports the role of ultrasound-based body contouring and radiofrequency-based skin tightening techniques as valuable options for addressing localized fat deposits and improving body contour.

Various modalities exist for body contouring through weight loss or amelioration of abdominal obesity. According to Clinical Practice Guidelines for Obesity 2022 in Korea, lifestyle modifications, including diet and exercise, should be prioritized. Pharmacological interventions may follow when necessary15. For cases of severe obesity or obesity accompanied by complications, with a BMI of 35 kg/m2 or more, or a BMI of 30 kg/m2 or more with obesity-related comorbidities, who have failed to lose weight with non-surgical treatment, bariatric surgeries such as laparoscopic sleeve gastrectomy (LSG), laparoscopic Roux-en-Y gastric bypass (LRYGB), biliopancreatic diversion with duodenal switch (BPD/DS), and laparoscopic adjustable gastric banding (LAGB) are indicated16,17,18. Additionally, intragastric balloon placement can be contemplated19,20. However, physicians could consider non-surgical approaches as part of comprehensive body contouring strategies and also, patients seeking aesthetic improvements without invasive surgery may find these procedures appealing. Among the techniques available, liposuction aims to reduce localized adipose tissue. The findings of this study suggest that ultrasound-based body contouring and radiofrequency-based skin tightening techniques are noninvasive and could be beneficial for female patients with abdominal obesity.

In comparison to prior studies using radiofrequency and/or ultrasound device, our research demonstrates similar trends in waist circumference reduction21,22,23. Furthermore, this study holds a distinct advantage as it employs fat CT scans to assess abdominal fat area, allowing for precise pre- and post-treatment comparisons. Our findings that visceral fat (with an average reduction of only 1.48 cm² or 1.46%) was not significantly affected while superficial fat showed significant reduction (18.90 cm² or 7.19% decrease) provide important insights into the selective targeting of these technologies. This methodological approach enhances the reliability and accuracy of our findings, marking a significant strength of this pilot investigation.

This study has several limitations that should be addressed. Firstly, the small sample size(9 female participants) and pilot nature of the study necessitate further research with larger, more diverse populations. Randomized controlled trials (RCTs) could provide higher levels of evidence. Secondly, the follow-up period in this study was relatively short, limiting the evaluation of long-term effects and safety. Therefore, long-term follow-up studies are essential to assess sustained efficacy and potential adverse effects. Thirdly, this study was conducted at a single center with participants exclusively from Korea, which may limit the generalizability of the findings to other populations. Cultural, demographic, and physiological differences could influence the outcomes of similar interventions in broader or more heterogeneous populations. Future studies should aim to include multi-center designs and diverse participant groups to enhance external validity. This version integrates the additional limitation regarding the single-center design and Korean participants while maintaining a professional and academic tone. It also emphasizes the need for future research to address these limitations.

From a technical standpoint, the variability in ultrasound and radiofrequency equipment should be considered, as different devices and protocols may produce varying results. Further research is needed to optimize treatment protocols, including the frequency, intensity, and duration of treatment, to determine the most effective combination.

Comparative studies are also crucial. Evaluating ultrasound and radiofrequency treatments against other non-invasive body contouring methods, such as cryolipolysis and laser lipolysis, will help to assess their relative efficacy. Additionally, comparing these non-surgical methods with surgical options like liposuction and body lifts can elucidate the advantages and limitations of non-invasive approaches.

Patient satisfaction and quality of life assessments are important components that should be included in future studies. Understanding the psychological impact of non-invasive body contouring on patient satisfaction, self-esteem, and mental health is crucial. Moreover, conducting a cost-effectiveness analysis will provide insight into the economic benefits of these treatments from a healthcare perspective.

Other physiological effects should also be explored. Further research should evaluate the impact of non-invasive body contouring methods on metabolic health, including changes in insulin sensitivity and lipid profiles. Investigating the effects of ultrasound and radiofrequency treatments on inflammation and fibrosis within adipose tissue is also important to understand the long-term physiological implications.

Nevertheless, this pilot study provides a foundation for future clinical trials. Researchers should explore larger sample sizes, extend follow-up periods, and include additional outcome measures in subsequent studies. Comparative studies with other body contouring methods will also be valuable in informing clinical practice and determining the relative efficacy and benefits of these non-invasive procedures.

Conclusion

In conclusion, ultrasound-based body contouring and radiofrequency-based skin tightening techniques can be effective for reducing abdominal circumference and subcutaneous fat volume in Korean women, with our data showing significant reductions in waist circumference (3.83 cm or 4.35%) and superficial fat area (18.90 cm² or 7.19%). The finding that visceral fat was not significantly reduced (1.48 cm² or 1.46%) suggests these techniques primarily target subcutaneous rather than visceral fat deposits. However, these initial results highlight the need for more rigorous studies with larger sample sizes, diverse populations, and longer follow-up periods to establish clinical efficacy and safety. Future research should focus on optimizing treatment protocols, conducting comparative studies with other body contouring methods, and assessing the long-term physiological and psychological impacts of these non-invasive procedures.