The Beltline and Beyond: A Review of Minimally Invasive Body Contouring Modalities

Body contouring refers to the use of surgical or non-surgical interventions to modify the shape of the body, most commonly targeting adipose tissue.  While tumescent liposuction is the most popular means of body sculpting, there is rapidly growing interest in minimally invasive body contouring technologies^1,2. These include cryolipolysis, laser therapy, radiofrequency, ultrasound, and High Intensity Focused Electro-Magnetic Technology (HIFEM).

The following report will review treatment classes, their mechanism of action, treatment protocols and potential adverse events.

Cryolipolysis

Cryolipolysis borrows the concept of cold-induced panniculitis, delivering targeted, controlled cooling to the subcutaneous layer to induce selective adipocyte apoptosis^3,4.  Histological assessment shows cool-induced adipocyte damage peaks at 14 days and is subsequently cleared by macrophages through an inflammatory process which lasts up to 3 months^2,3,5

The most commonly used technology in North America is CoolSculpting^® (ZELTIQ Aesthetics, Inc., Pleasanton, CA, USA), approved for treatment of the flanks, abdomen, submentum, upper arms, bra fat, and medial thighs^2,5. Subcutaneous fat is cooled to -10°C for 35 to 60 minutes based on the anatomic area.  

Fat reduction ranges from 14-25.5% per treatment^6-8.  Localized areas of fat accumulation tend to respond better given the nature of the applicator².Treatment response is typically seen at 3 weeks post-procedure but may continue for up to 6 months³. 

Cryolipolysis is overall well tolerated.   Initial cold-associated discomfort subsides after 5-10 minutes of treatment⁹.  Erythema, edema, ecchymosis and delayed onset pain may occur post-treatment lasting from a few days to weeks⁹.  Rare side effects such as paradoxical adipose hyperplasia (PAH) occur in 0.0051-0.021% of cases but may be underreported^10,11.  There is a disproportionate number of cases among Hispanic males seeking abdominal and chest treatment, potentially related to anatomic sexual dimorphism¹¹. 

Cryolipolysis provides an effective treatment option for fat reduction with high levels of patient satisfaction¹².  Skin laxity may improve through normal elastic recoil properties but more commonly a secondary intervention is required to address skin laxity¹³.

Laser-assisted Lipolysis

Laser-assisted lipolysis uses a 1060-nm diode laser that triggers heat-mediated inflammation to induce adipocyte apoptosis (SculpSure^® Cynosure, Westford, MA, USA).  Treatment temperatures selectively target adipocytes at 42-47°C which disrupts cell membrane integrity and fat is eventually cleared from the interstitial space^14,15.  The device’s contact cooling system is necessary to preserve the integrity of the skin and adnexae, preventing potential thermal complications².  

Laser lipolysis is indicated for fat reduction of the abdomen, flanks and submentum – it does not address skin laxity.  The ideal treatment duration for 1060-nm is targeted to 20 and 25 minutes to avoid undertreating, or subcutaneous nodules if heated too long².  

Slimmer abdomens and pinchable fat respond best to treatment with reduction of 11.5% reported with a single treatment².  Anecdotally, patients require 1-3 sessions with improvement seen 3 months post-procedure².  Tolerability is favourable – mild to moderate tenderness lasting up to 2 weeks is common¹⁶.  

Magnetic Resonance Contouring 

High intensity focused electromagnetic technology (HIFEM) is the newest technology for body contouring, inducing fat reduction and potentially improving muscle thickness, strength and tone¹⁷.  

HIFEM technology was initially approved for contouring of the abdomen and buttocks (EMSculpt^®, BTL Industries, Inc., New York, NY, USA).  Electromagentic energy is used to stimulate 20 000 supramaximal muscle contractions during a 30-minute treatment session^18,19.  The high level of contractions may stimulate lipolysis which releases a large amount of tissue-damaging free fatty acids into the surrounding fat to induce adipocyte apoptosis²⁰ demonstrated by a 91.7% increase in the adipocyte apoptotic index in 120 histologic samples¹⁸.  

The major differentiator with HIFEM technology is the resultant effect on muscle tissue.  A recent study showed an 18.6% reduction of adipose tissue thickness, 15.4% increase in rectus abdominis muscle thickness, and 10.4% reduction in diastasis recti¹⁸.  Positive results have also been reported for gluteal toning and lifting as well as with a secondary device (Emsella^®, BTL Industries, Inc., New York, NY, USA) for urinary incontinence^19,21.

Treatment protocols include a minimum of four 30-minute sessions over 2 weeks and a single maintenance treatment session performed every 3 to 6 months¹⁸.  Treatment is well tolerated with rare reports of painful, gripping muscle contractions or brief electric shocks¹⁸. Contraindications to treatment include pregnancy, metal or electronic implants.

The ideal HIFEM patient has not been established.  Patients who respond best to treatment typically have a low to medium BMI and less than 2.5cm of pinchable fat^18,19.  This is likely due to the distance between the EM coil and target tissue^18,19.  It is unclear if HIFEM is suitable to treat visceral fat.  Lastly, skin laxity is not targeted with HIFEM technology. 

Radiofrequency

Radiofrequency treatment is most commonly associated with skin tightening, and more recently, fat reduction²².   Volumetric heating and tissue impedance selectively target collagen-rich tissue to induce tissue remodeling and tightening over 60-90 days²³.  Adipocyte apoptosis and fat reduction occur through this bulk heating process¹⁷. 

Radiofrequency heats tissue to 43-45°C for up to 45 minutes, followed by epidermal cooling to reverse the thermal gradient¹⁷.  Tissue cooling is an essential component in order to avoid complications such as burns, infection, scarring and dyspigmentation¹⁷.  Treatment is generally well tolerated with heat-related discomfort noted at the time of the procedure.  Topical anesthetic is not recommended and may enhance dermal sensitivity and interfere with penetration of RF waves¹³. Transient erythema and edema lasting 24 hours may occur²⁴.  Rare side effects such as dysesthesia, fat atrophy, subcutaneous nodule formation are reported²⁴.  

There are now a number of radiofrequency devices indicated for body contouring.  Vanquish^® (BTL Industries, Boston, MA, USA) is a monopolar radiofrequency device used for fat reduction of the mid-section.  Its novel panels placed 1 cm above the skin allow contactless treatment of a large surface area, decreasing the overall treatment time and potentially the number of treatment sessions, making it a suitable option for patients with elevated BMI (i.e. >25)^{2, 25, 26}  

truSculpt^® (Cutera, Brisbane, CA, USA) is another monopolar RF device with various size hand pieces that allow flexible treatment of both small and large areas. The Venus Legacy^® (Venus Concept, Toronto, ON, Canada) combines multipolar RF and-or pulsed electromagnetic fields to promote either skin tightening or fat reduction depending on the applicator used, allowing increased versatility.  Pulsed EM stimulates angiogenesis and growth factor release to induce collagen formation through a non-thermal mechanism.  

Patients with low to moderate BMI and presence of skin laxity tend to be ideal candidates for this class of technology¹⁷.

Ultrasound

Ultrasound technology has been used in medicine for many years for ablation of renal calculi, cardiac ablation and ablation of various benign and malignant tumors¹³.  Two classes of ultrasound are used for body contouring.

The first class (Ultrashape, Syneron Candela) uses low-intensity/low frequency nonthermal pulsed ultrasonic waves to induce cavitation at specific depth resulting in fat cell lysis²⁷.  The absence of thermal effect limits its effect on collagen and skin tightening.  Studies have shown its efficacy in treating focal adiposity of the abdomen, hips and thighs in nonobese patients (BMI < 30)^27,28.  The recommended protocol involves 3 treatments at 2-week intervals. A single treatment yields a mean reduction in waist circumference by 1.3–2.5 cm^27-29.   Three treatments reduced waist circumference by 2.3–3.5 cm^27,29. 

The second class (Liposonix, Solta Hayward, CA, USA) uses highly convergent energy to deliver heat at 56°C to a focal zone known as High-Intensity Focused Ultrasound (HIFU), inducing coagulative necrosis, adipocyte apoptosis and neocollagenesis¹³. HIFU may also induce ultrasonic cavitation of adipocytes. HIFU has been evaluated for treatment of focal adiposity of the abdomen, waist, hips, outer and inner thighs, and buttocks, and in male breast hypertrophy^30,31.  A single treatment is typically sufficient¹³. Total treatment time is 45-60 minutes involving two to 3 passes over the target area³¹.  Mean reductions in waist circumference range from of 4.2 to 4.7 cm 12 weeks post- procedure^30,31.  

Clinical improvement with ultrasound contouring is typically noted by 2 weeks and continues up to 12 weeks for both classes of treatment^30-32.  Treatment-associated symptoms include pain during and post-treatment, ecchymoses, erythema and dysesthesia^28-32. Severe adverse events such as burns, blisters or scars were not reported.

Discussion

Minimally invasive body contouring procedures continue to gain traction in aesthetic dermatology as patients seek effective treatments with limited recovery and low risk of adverse events.  These treatment modalities offer options for non-obese patients seeking modest to moderate improvement. None of the named technologies induce changes in lipid profile or liver enzymes.  The success of these treatments is largely based on a comprehensive clinical assessment, understanding of the various modalities, and where combination therapy may be necessary.  Identification of the contributory changes in the treatment area – increased fat, skin laxity, cellulite or volume loss – should ultimately guide therapeutic decision-making.  Discussion around treatment expectations is key, including anticipated clinical outcomes, time to improvement and need for maintenance therapy.