The increasing prevalence of obesity is a major global public health challenge. Excess body weight significantly increases the risk of a number of chronic diseases, such as type 2 diabetes mellitus, non-alcoholic fatty liver disease, hypertension, and cardiovascular disease, including myocardial infarction and stroke. Obesity is also strongly associated with a wide range of health problems, including osteoporosis, joint disease, renal dysfunction, dyslipidaemia, obstructive sleep apnoea, and certain cancers. It can also lead to musculoskeletal problems and rapid cognitive decline. Obesity results from the complex interaction of many etiopathogenetic factors, including logical, and environmental factors. The hedonic aspect of eating, characterised by strong cravings and challenges in resisting certain foods, adds another layer of complexity to the problem. Conventional treatments are sometimes ineffective. Transcranial magnetic stimulation (TMS), a non-invasive method of modulating brain activity, is emerging as a promising new treatment for obesity and associated eating disorders.
This article explores the potential of magnetic therapy, specifically transcranial magnetic stimulation (TMS), as a weight loss solution. We will explore the evolution and development of transcranial magnetic stimulation and present the results of recent randomized clinical trials conducted in obese subjects. These suggest that repetitive transcranial magnetic stimulation and deep transcranial magnetic stimulation may be effective in reducing body weight, BMI and food cravings. TMS targets specific brain regions involved in the regulation of intense food cravings and dietary control and has shown promise in facilitating weight loss. The neural circuits involved and the underlying mechanisms of action of this neurostimulation technique are also reviewed.
Understanding Transcranial Magnetic Stimulation (TMS)
TMS employs electromagnetic induction to elicit localized electrical currents within the brain, thereby modulating neuronal activity. Initially developed to treat stubborn psychiatric conditions such as mood disorders, substance abuse, and post-traumatic stress disease, the application of TMS has subsequently expanded to encompass a range of neurocognitive disorders such as schizophrenia, dementia, and eating disorders. Repetitive Transcranial Magnetic Stimulation (rTMS) and deep Transcranial Magnetic Stimulation (dTMS) constitute the core methodologies within the TMS framework.
The rTMS protocol employs a figure-of-eight electromagnetic coil to generate focal magnetic pulses or sequences of pulses that target discrete cortical regions to a depth of approximately 1.5 cm below the scalp. These magnetic pulses can modulate cortical excitability, either augmenting or diminishing the electrical activity within the targeted neuronal circuits. Conversely, dTMS is characterised by the use of an H-coil, which is designed to extend stimulation to both cortical and subcortical structures, achieving penetration depths of 4.5 to 5.5 cm from the cranial surface. In both rTMS and dTMS modalities, the use of high-frequency stimulation (≥5 Hz) is associated with an excitatory effect on neuronal excitability, whereas low-frequency stimulation (≤1 Hz) is associated with inhibitory effects. Further diversification within TMS techniques includes intermittent theta burst stimulation (iTBS) and continuous theta burst stimulation (cTBS). iTBS, characterised by its high-frequency burst pattern, is postulated to induce an increase in cortical excitability, whereas cTBS is associated with a decrease in cortical excitability. As it has been reported, these stimulation protocols have been found to provide a range of modulatory effects on neural circuits, which highlights the potential usefulness of TMS in the therapeutic modulation of neurocognitive and neuropsychiatric conditions.
TMS is highly valued within the clinical paradigm for its ability to induce lasting therapeutic changes beyond the temporal limits of the stimulation sessions themselves. The significance of the neurophysiological changes induced by TMS is highlighted by its capacity to induce long-term synaptic plasticity. Further, rTMS can be classified into single-session and multi-session approaches. The former, a single-session application, is extensively employed in experimental research to evaluate the immediate neurophysiological effects of rTMS. The efficacy and specificity of TMS interventions depend on the precise localization of the targeted brain region. Electroencephalography (EEG) or structural magnetic resonance imaging (MRI), are necessary for this purpose. These techniques should be complemented by neuronavigation technologies, a methodology that has been extensively documented in the literature. Precision in targeting is essential to optimize the therapeutic outcome of TMS. TMS is considered a safe and non-invasive method that is generally well-tolerated. However, it has been reported that the incidence of side effects was approximately 5%. The most common were headache (46%), lightheadedness (22%), muscle twitching (10%), and a general feeling of lightheadedness (10%).
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How TMS Works for Weight Loss
TMS is a potential intervention for modifying neural circuits that are essential for controlling appetite, reducing food cravings, and regulating impulses. These components are closely linked to the development and treatment of obesity. These investigations suggest that obesity may result from imbalances in brain networks, with some pathways associated with gratification mechanisms and others involved in cognitive control and impulse inhibition. The increasing importance of neural function and control mechanisms in weight management, beyond metabolic or lifestyle factors, is now recognised. In particular, the dorsolateral prefrontal cortex (dlPFC) is a key neural site for modulating hunger and satiety signals and plays an essential role in regulating impulses and food choices. This region has become a specific target of neurostimulation techniques for addictive behaviours and eating disorders because of its role in the executive functions that manage the cognitive regulation of food consumption. However, the specific cognitive mechanisms affected by the dlPFC that are modulated by TMS remain largely undefined. It has been theorised that such dynamics may include changes in reward valuation, attentional biases, or inhibitory control.
By using electromagnetic pulses to stimulate targeted areas of the brain, the treatment helps regulate mood and behavior. The process involves placing a specialized coil over the scalp that sends out electric pulses. The energy from the pulses can reach deep into the brain, activating specific regions that help modulate emotions and behaviors. It's believed that TMS Therapy works by altering the way specific brain circuits function, which can lead to an improved mood and decreased cravings for food. TMS can help people manage stress more effectively, which can contribute to healthier eating habits. Studies have also shown that TMS can help to motivate and increase physical activity levels, leading to further weight loss. By stimulating the parts of the brain responsible for regulating appetite, TMS can help people who struggle with emotional eating or unhealthy snacking habits.
TMS vs. Other Weight Loss Methods
TMS Therapy is a relatively new weight loss treatment that has shown promising results in recent years. Unlike other weight loss treatments, such as diet and exercise, TMS does not require significant lifestyle changes. Patients can usually carry on with their regular daily routine while undergoing treatment. TMS is entirely non-invasive and no recovery time is required. The procedure is relatively quick and painless, and patients can return to their daily activities immediately. The most significant advantage of TMS Therapy is that it offers a safe, effective solution for those struggling to lose weight despite trying other methods. By targeting the source of the problem - your brain - TMS Therapy can give you the push you need to reach your weight loss goals without relying on dangerous or drastic measures. The bottom line is that TMS Therapy offers a safe, non-invasive way to help manage eating behaviors and cravings. For many, it can produce lasting lifestyle changes and support weight loss efforts long-term.
Research on TMS for Weight Loss
This section will provide an overview of studies investigating the effects of TMS in obese individuals. The focus will be on two specific TMS techniques, rTMS and dTMS. modulation techniques with sham interventions to determine the impact of such stimulations on key indicators of interest in the field of obesity research.
rTMS Studies
According to a study conducted by Kim and colleagues in 2018, 57 individuals between the ages of 18 and 65 were randomly assigned to two groups in a two-week, single-blind trial. Of the participants, 29 received rTMS, while 28 received sham treatment. The rTMS sessions, each lasting 20 minutes at a frequency of 10 Hz, targeted the left dlPFC.
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Continuing from the previous study, the research group conducted a four-week study on 43 patients who were classified as obese and aged between 18 and 70. The participants were divided into two groups: 21 individuals received eight 20-minute sessions of rTMS at 10 Hz, while the remaining 22 individuals received sham treatments. The study results indicate that individuals who received rTMS treatment experienced a significantly greater weight loss (2.75 kg, SD 2.37) compared to those who received the sham treatment (0.38 kg, SD 1.0). Furthermore, the rTMS group also showed significant reductions in fat mass and visceral adipose tissue by the fourth week.
In a study conducted in 2019, the effects of combining rTMS with a low-carbohydrate diet were tested on 37 overweight or obese patients. The participants were randomly assigned to two groups: 18 followed the diet with rTMS, and 19 followed the diet with sham rTMS.
In 2020, a study was conducted on 29 obese Filipino patients aged between 15 and 65. The patients were randomly assigned to either a treatment group (15 subjects) or a sham group (14 subjects). They received four 20-minute rTMS sessions at 10 Hz to the left dlPFC over two weeks in a single-blind, monocentric setting. Upon completion of the study, the treatment group exhibited a significant decrease in BMI (-0.6, SD 0.6) and body weight (-1.3 kg, SD 1.3).
dTMS Studies
A pilot study was conducted on 33 obese individuals (9 men, 24 women, mean age 48.1 years, SD 10.6). The participants were divided into three groups: 13 underwent a 5-week high-frequency dTMS treatment (18 Hz; HF group), 10 received low-frequency dTMS (1 Hz; LF group), and 10 received placebo treatments (sham group). The stimulation targeted the bilateral Prefrontal Cortex (PFC) and Insula, consisting of 15 sessions, each lasting 30 minutes. Food cravings, metabolic indicators, and neuroendocrine measures were assessed at baseline, after 5 weeks of treatment, and at follow-up sessions (1 month, 6 months, and 1 year post-treatment). The findings showed a significant decrease in both body weight (-7.83 kg, SD 2.28) and BMI (-2.83, SD 0.83) in the HF group compared to the sham group. Additionally, there was a significant trend towards reduced food cravings in the HF group compared to the LF and sham groups.
In another study involving 22 obese individuals (17 female; mean age 44.9 ± 2.2 years; BMI 37.5 ± 1.0 kg/m2), the same researchers suggested that dTMS may have the potential to influence both the pathways of the brain-gut communication and the composition of the gut microbiome. The study involved randomising participants into three groups, each attending 30-minute sessions three times a week for five weeks. They received either high-frequency (18 Hz - HF), low-frequency (1 Hz - LF), or sham dTMS treatments, respectively, with the stimulation site being the bilateral PFC and Insula. After 5 weeks, the HF group showed significant weight loss compared to the LF and sham groups (HF: -4.1 kg, SD 0.8 vs. LF: -1.9 kg, SD 0.8 vs. sham: -1.3 kg, SD 0.6).
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A preliminary randomized, double-blind, placebo-controlled study was conducted to investigate the resting-state functional connectivity (rsFC) in obese patients after 15 sessions of 30-minute treatments. Nine participants underwent high-frequency (18 Hz - HF) dTMS treatment, focusing on the bilateral PFC and Insula, three times a week for five weeks, while 8 were given placebo treatments (sham TMS group). Out of the 17 participants, 6 were diagnosed with Type 2 Diabetes (T2D). The results indicate that the experimental group experienced a significant decrease in body weight and BMI, which persisted through a one-month follow-up. Additionally, there was an observed enhancement in the functional brain connectivity within the medial Orbitofrontal Cortex (mOFC), coupled with a reduction in connectivity with the occipital pole.
A study was conducted to examine the correlation between psychological symptoms and neuroendocrine parameters in individuals with obesity. The study also investigated the effects of a 5-week treatment regimen involving 30-minute high-frequency (18 Hz) stimulations targeting the bilateral PFC and Insula using dTMS.
A study was conducted on 45 patients who were obese, out of which 33 were female. The patients had an average age of 48.8 years (SD 9.9), body weight of 97.6 kg (SD 14.2), and BMI of 36.2 (SD 4.2). The patients were randomly assigned to two groups, out of which 26 patients received high-frequency (HF) dTMS, while 19 underwent sham stimulation. The study found that the HF group showed a significant reduction in body weight and BMI, along with a decrease in impulsivity levels. Additionally, a positive correlation was observed between decreased impulsivity and leptin levels.
The Role of Food Cravings
These studies suggest that both TMS methods are effective in reducing body weight and BMI, with high-frequency stimulation of the dlPFC showing particular promise, which is in line with previous research. However, further research is required to investigate the effects on food cravings. The current evidence suggests that by reducing the frequency and intensity of food cravings, it may be possible to decrease calorie intake and facilitate fat loss. In other words, by strengthening cognitive regulatory competencies, individuals may be better equipped to exercise discipline in their dietary practices. This enhancement provides the opportunity to choose healthier food options instead of those prompted by impulsive or emotional consumption patterns, which can aid in the weight loss process. The phenomenon of craving, characterized as an intense and uncontrollable urge to consume, is believed to be influenced by dysfunction in frontostriatal brain circuits that are involved in both substance abuse and overeating. High-frequency rTMS can selectively activate dlPFC while reducing activity in deeper regions such as the orbitofrontal cortex (OFC) and anterior cingulate cortex (ACC).
However, the effects of TMS on food cravings appear to be a topic of debate, with some studies highlighting the ambiguity of treatment responses. A study was conducted to evaluate the effectiveness of high-frequency rTMS targeting the left dlPFC in reducing food cravings in a group of 28 female participants. Both real and sham rTMS sessions were administered before and after participants were exposed to highly palatable foods. The results indicated that self-reported craving remained unchanged after the real rTMS treatment but increased in the sham condition. However, it should be noted that no significant variations in snack consumption were observed during the brief 5-minute post-stimulation period, regardless of the type of rTMS administered. In another study, the effect of rTMS on the left PFC in 10 healthy women was investigated using an improved …
Potential Side Effects of TMS Therapy
TMS Therapy is a safe and effective weight loss treatment option with minimal side effects. The most common side effects reported from TMS Therapy are mild, such as headaches and tingling sensations. Other side effects may include jaw pain, scalp discomfort, and nausea. Most of these go away as a person adjusts to the treatment. Overall, the potential side effects of TMS Therapy are generally mild and do not pose a significant risk for most people considering this form of treatment. Before beginning treatment, it is essential to talk to your doctor about any potential side effects that could occur with this type of therapy.
Caution: Magnetic Rings and Other Magnetic Devices
It's easy to be tempted by products touting quick and easy ways to lose weight, such as magnetic rings for weight loss. But generally, if a weight loss gimmick sounds too good to be true, it probably is. There is no solid evidence that magnetic therapy will help you lose weight. Magnetic rings are placed on your finger, but many other products are sold for magnetic weight loss therapy, such as:
- Magnetic bracelets
- Magnetic toe rings
- Magnetic earrings
- Magnetic patches
- Magnetic “seeds” worn on the outer ear
These devices are “purported to increase your metabolism through the north pole of the magnet. Some people also suggest that the rings and bracelets can be used in combination with acupressure,” an alternative therapy technique, based on the idea that stimulating certain points on the body will lead to changes within the body. There's no evidence to support the use of magnetic therapy for weight loss. A research study in 2019 found that noninvasive electromagnetic brain stimulation, combined with increased exercise and reduced calorie intake, can help people with overweight lose weight. A more recent review article of previous research also concludes that noninvasive brain stimulation techniques may help with weight loss and reducing food cravings. These studies may have made people think magnets might enhance their weight loss journey, but electromagnetic brain stimulation is not the same as wearing static magnetic jewelry. There is zero evidence to suggest that magnetic rings, or similar magnetic devices, aid in weight loss.
Magnetic rings might interact with imaging tests and medical devices. Wearing acupressure magnets (or any magnet) can be very harmful or compromise test results if you have a magnetic resonance imaging (MRI) test, which your doctor might prescribe if you have certain conditions. The possibility of creating a magnetic projectile, combined with risk to the machine are why there are very strict rules regarding magnets in the scan room. Magnetic rings may also be harmful to people who wear devices such as pacemakers, which regulate heart rhythm. Speak with your doctor if you have any medical devices before trying any magnetic jewelry. Note that any kind of small magnet, including magnetic jewelry, may pose a hazard to small children if swallowed.