An Introduction to Fat Reduction

Public awareness of health problems associated with obesity, combined with popular trends towards achieving physical beauty, has given rise to a demand for fat reduction and body contouring treatments that are effective, safe, affordable and have minimal downtime. Liposuction has been indicated in many studies to be very effective, however, it carries a relatively high risk of complications and side effects¹ with reports of long-term and even fatal difficulties due to complications during and after treatment.² Non-surgical aesthetic procedures offer a lower-cost and safer alternative with a shorter recovery time. It is therefore not surprising that demand for these treatments has grown by more than 500% since 1997 and that they account for 80% of total cosmetic procedures in the US.³

Non-invasive fat reduction

Non-invasive fat reduction therapies are often classified as either ablative (cooling, heating, adipocyte disruption or dissolution) or non-ablative (lipolytic stimulation or ultrastructural modification). The ablative treatments cause adipocytes to shed triglycerides and result in apoptosis, necrosis or reduced cell size. Non-ablative therapies leave adipocytes intact.⁴ The most commonly used non-invasive treatments for fat reduction include: cryolipolysis, low level laser therapy (LLLT), radiofrequency (RF), high-intensity focused ultrasound (HIFU) and injection lipolysis.

Patient selection

• In general, three types of patients undergo body contouring procedures:
  
• Patients wanting to treat focal adiposity in problem areas such as the abdomen, thighs, or hips 
  
• Patients with skin laxity of the face, neck, or arms wanting to tighten skin and deeper layers
  
• Patients requiring treatment that combines both fat reduction and skin tightening⁵
  

These treatments are most ideal for non-obese (body mass index of less than 30) patients seeking modest localised fat reduction. With a BMI of more than 30, patients often have visceral fat, which increases cardiovascular and other health risks.⁶ These patients benefit much more from global weight reduction initially, followed by tightening of loose skin and contouring. When selecting patients, it is important to thoroughly discuss their motivations for treatment and gain an appreciation of their social and psychological wellbeing during the consultation.

Types of treatments

Cryolipolysis

Cryolipolysis is growing in popularity and works by controlled cooling causing adipocyte apoptosis. One cryolipolysis device, CoolSculpting, has been approved by the Food and Drug Administration (FDA) for the treatment of the flanks, abdominal area and thigh fat.⁴ The devices for cryolipolysis usually contain a cup-shaped applicator that is applied to the treatment area causing tissue to be drawn into the handpiece under vacuum. Each area is treated for approximately 45 minutes and then massaged to quicken recovery. Results are generally seen within three days of treatment with full effects visible at three to four weeks.⁷ The number of treatment cycles is dependent on the treatment area and patient: the flanks typically require one treatment, whilst abdomen and thighs often require two or more. Treatments should be spaced eight weeks apart to allow sufficient recovery time between procedures.⁸

High-intensity focused ultrasound

This modality uses high frequency focal acoustic energy to raise the temperature around adipose tissue and produce coagulative necrosis.⁹ HIFU has a focal point depth of 1.3cm and therefore patients need adipose tissue depth of at least 1cm beyond the focal point. The HIFU LipoSonix device has been approved by the FDA for the reduction of waist circumference.10 The procedure typically involves placing the HIFU device two or three times on the treatment area, each time taking 15 to 20 minutes, for a total treatment time of 45 minutes to one hour. The clinical response is usually evident within two weeks and complete within three months. A study by Jewell et al supports mean reductions in waist circumference ranging from of 4.2-4.7cm, 12 weeks after the procedure.⁸

Radiofrequency

Radiofrequency causes thermal injury to targeted tissue layers using electrical energy.¹¹ Monopolar and multipolar forms are available for fat reduction. In monopolar radiofrequency devices, energy is passed from a single electrode into the tissues and directed to a return pad in another area of the body. In multipolar radiofrequency, two or more electrodes within the same handpiece are positioned at different points on the skin so that the waves pass between them to create a heating effect.¹² Radiofrequency devices have traditionally been used for tightening of the skin and targeting wrinkles but are also used for fat and cellulite reduction.⁵ Targeted body sites include the abdomen, thighs, buttocks, extremities and face.⁴ Reductions in fat volume are typically seen three to eight weeks after treatment, with up to 3cm reductions in waist circumference following 10 treatments.¹³ Radiofrequency can present challenges in terms of pain management. Topical anaesthetics that numb the epidermis are not recommended as they may aggravate pain, whilst local anaesthetics may interfere with delivery of radiofrequency waves.¹⁴ Oral analgesics are the generally recommended agents for pain management.⁸ 

Low level laser therapy

LLLT utilises non-thermal ablation of adipocytes for focal adiposity and skin tightening. It can be used for the abdomen, thighs, flank and neck, requiring up to eight sessions for optimal effect. Laser light is applied to areas with excess fatty tissue for five to 10 minutes per region with total procedure time of approximately 30 minutes.¹⁵ It takes up to three weeks to see the final results.⁷ A trial by Jackson et al¹⁶ demonstrated a reduction of 2.6cm in waist circumference following LLLT over a two-week treatment period.

Injection lipolysis

Injection lipolysis is used for focal adiposity and skin tightening around the face, abdomen, hips, thighs and flanks.⁷ Prior to the procedure, topical or injectable local anaesthetic is applied, and an injection consisting of phosphatidylcholine with deoxycholic acid is then delivered using a 4-6mm needle.¹⁷ Three to 15 treatment sessions are usually required, with optimal effect seen at four to six weeks. The addition of a ‘detergent’ such as deoxycholic acid, causes fat cell destruction. This aims to prevent fat cells from refilling over time and reduces the number of treatments required. The mechanism of action for the treatment is not fully understood.

Complications and side effects

Non-invasive fat reduction therapies are generally very safe, with most patients reporting only mild and transient adverse effects. The most commonly reported side effects are mild discomfort, erythema and oedema, with the majority of patients having little downtime. A decrease in sensation in the treatment area for up to eight weeks is reported in around two-thirds of patients treated with cryolipolysis¹⁸ and rarely with injection lipolysis, due to direct nerve injury.¹⁹ Paradoxical adipose hyperplasia (PAH) is also a rare complication of cryolipolysis; typically appearing two months post-treatment with an incidence of one in 20,000 treated patients.²⁰ Rare adverse events following radiofrequency treatment include scars, burns, purpura, oedema, hyperpigmentation and blisters.²⁰ LLLT treatments are generally thought to have the fewest and most mild complications with several studies reporting no adverse effects at all.^{1,20,21,22,23}

Clinical effectiveness

A number of studies support the effectiveness of these therapies for reducing subcutaneous fat tissue, with a degree of efficacy dependent on body-site.^8,11,14,24 Owing to the heterogeneity of studies, it is difficult to compare efficacy between modalities. Nevertheless, there are reports of high patient satisfaction for these procedures: LLLT carries patient satisfaction rates as high as 80%;²⁵ studies on cryolipolysis report patient satisfaction at 73%- 100%;¹ while RF and HIFU studies identify patient satisfaction at 97% and 85% respectively.^26,27 A study by Reeds et al indicated that patients receiving phosphatidylcholine and deoxycholate injections on subcutaneous fat were highly satisfied with the treatment protocol.²⁸

Conclusion

There is increasing patient demand for non-invasive fat reduction and body contouring treatments, which offer a quicker, low-cost and safer alternative to liposuction. Appropriate patient selection and thorough pre-procedural assessment is essential in order to select the optimal treatment strategy for the patient and achieve the best outcomes. All discussed therapies have a good safety profile, but nevertheless, practitioners should undergo appropriate training and be aware of potential complications and subsequent management options. Future studies should use standardised, agreed outcome measures so that results between modalities can be more accurately compared.