Effects of auricular stimulation on weight- and obesity-related parameters: a systematic review and meta-analysis of randomized controlled clinical trials

Background

Over the last three decades, the number of randomized controlled trials (RCTs) using stimulation of auricular vagal sensory nerves by means of electrical stimulation, auricular acupuncture, or acupressure to support weight loss has increased markedly. This systematic review focuses on the effects of auricular stimulation (AS) on anthropometric parameters and obesity-related blood chemistry.

Methods and analysis

The following databases were searched until November 2021: MEDLINE (PubMed), EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), ISI Web of Science, and Scopus Database. Data collection and analysis were conducted by two reviewers independently. Quality and risk assessment of included studies was performed using the risk of bias tool of the Cochrane Handbook, and the meta-analysis of the effect of the most frequently assessed biomarkers was conducted using the statistical software RevMan.

Results

The full texts of 1,274 studies were screened; 22 contained data on obesity-related outcomes, and 15 trials with 1,333 patients were included in the meta-analysis. The overall quality of the included trials was moderate. AS significantly reduced body mass index (BMI) (mean difference (MD) = -0.38 BMI points, 95% CI (-0.55 to -0.22), p < 0.0001), weight (MD = -0.66 kg, 95% CI (-1.12 to -0.20), p = 0.005), waist circumference (MD = -1.44 cm, 95% CI (-2.69 to -0.20), p = 0.02), leptin, insulin, and HOMA insulin resistance compared to controls. No significant reduction was found in body fat, hip circumference, ratio of waist/hip circumference, cholesterol, LDL, triglycerides, adiponectin, ghrelin, and glucose levels. The AS was safe throughout the trials, with only minor adverse reactions.

Conclusion

The study results suggest that a reduction of weight and BMI can be achieved by AS in obese patients; however, the size of the effect does not appear to be of clinical relevance. The effects might be underestimated due to active sham trials.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021231885.

Transcutaneous auricular vagus nerve stimulation as a novel therapy connecting the central and peripheral systems: a review

Currently, clinical practice and scientific research mostly revolve around a single disease or system, but the single disease-oriented diagnostic and therapeutic paradigm needs to be revised. This review describes how transcutaneous auricular vagus nerve stimulation (taVNS), a novel non-invasive neuromodulation approach, connects the central and peripheral systems of the body. Through stimulation of the widely distributed vagus nerve from the head to the abdominal cavity, this therapy can improve and treat central system disorders, peripheral system disorders, and central-peripheral comorbidities caused by autonomic dysfunction. In the past, research on taVNS has focused on the treatment of central system disorders by modulating this brain nerve. As the vagus nerve innervates the heart, lungs, liver, pancreas, gastrointestinal tract, spleen and other peripheral organs, taVNS could have an overall modulatory effect on the region of the body where the vagus nerve is widespread. Based on this physiological basis, the authors summarize the existing evidence of the taVNS ability to regulate cardiac function, adiposity, glucose levels, gastrointestinal function, and immune function, among others, to treat peripheral system diseases, and complex diseases with central and peripheral comorbidities. This review shows the successful examples and research progress of taVNS using peripheral neuromodulation mechanisms from more perspectives, demonstrating the expanded scope and value of taVNS to provide new ideas and approaches for holistic therapy from both central and peripheral perspectives.

Mechanism of Acupuncture in Treating Obesity: Advances and Prospects

Obesity is a common metabolic syndrome that causes a significant burden on individuals and society. Conventional therapies include lifestyle interventions, bariatric surgery, and pharmacological therapies, which are not effective and have a high risk of adverse events. Acupuncture is an effective alternative for obesity, it modulates the hypothalamus, sympathetic activity and parasympathetic activity, obesity-related hormones (leptin, ghrelin, insulin, and CCK), the brain-gut axis, inflammatory status, adipose tissue browning, muscle blood flow, hypoxia, and reactive oxygen species (ROS) to influence metabolism, eating behavior, motivation, cognition, and the reward system. However, hypothalamic regulation by acupuncture should be further demonstrated in human studies using novel techniques, such as functional MRI (fMRI), positron emission tomography (PET), electroencephalogram (EEG), and magnetoencephalography (MEG). Moreover, a longer follow-up phase of clinical trials is required to detect the long-term effects of acupuncture. Also, future studies should investigate the optimal acupuncture therapeutic option for obesity. This review aims to consolidate the recent improvements in the mechanism of acupuncture for obesity as well as discuss the future research prospects and potential of acupuncture for obesity.

Effects of auriculotherapy on weight and body mass index reduction in patients with overweight or obesity: Systematic review and meta-analysis

OBJECTIVE

Auriculotherapy is based on the stimulation of reflex points in the ear. However, little is known about its weight-reducing effects. The aim of the present systematic review and meta-analysis was to investigate the effects of auriculotherapy on weight and/or (BMI) reduction in overweight or patients with obesity.

METHODS

Twelve articles were selected for systematic review. Four randomized controlled trials (RCTs) investigating weight reduction and five investigating BMI reduction were selected for the meta-analyzes.

RESULTS

The results revealed an association between auriculotherapy and weight reduction (WMD, 1.507; 95% CI, 0.606-2.407; p < 0.000). Auriculotherapy was also significantly associated with BMI reduction (WMD, 0.865; 95% CI, 0.533-1.196; p < 0.004).

CONCLUSIONS

We found that auriculotherapy was effective in reducing weight and/or BMI in overweight or patients with obesity. However, the findings should be interpreted with caution due to heterogeneity.

Electric stimulation of ears accelerates body weight loss mediated by high-fat to low-fat diet switch accompanied by increased white adipose tissue browning in C57BL/6 J mice

Background

Weight reduction frequently occurs in patients receiving vagus nerve stimulation (VNS) therapy. Therefore, we hypothesized that during dietary intervention for weight loss, auricular electric stimulation (AES), an alternative of VNS, accelerates weight loss by increasing white adipose tissue (WAT) browning and increases energy expenditure.

Methods

C57BL/6J male mice were fed a high-fat diet for 5 wk. to induce obesity, then switched to a low-fat diet for 5 wk. and allocated into 3 groups to receive 2 Hz electric stimulation on ears, electrode clamps only, or nothing (AES, Sham and Ctrl, respectively).

Results

Switching to a low-fat diet reduced body weight progressively in all 3 groups, with the greatest reduction in the AES group. In accordance with a mild decrease in feed intake, hypothalamus mRNA levels of Npy, AgRP tended to be reduced, while Pomc tended to be increased by AES. Mice in the AES group had the highest concentrations of norepinephrine in serum and inguinal WAT, and expression levels of uncoupling protein-1 (UCP-1) and tyrosine hydroxylase in inguinal WAT. Furthermore, their subcutaneous adipocytes had multilocular and UCP-1⁺ characteristics, along with a smaller cell size.

Conclusion

AES, by increasing WAT browning, could be used in conjunction with a low-fat diet to augment weight loss in addition to suppressing appetite.

The History, Mechanism, and Clinical Application of Auricular Therapy in Traditional Chinese Medicine

Auricular therapy includes acupuncture, electroacupuncture, acupressure, lasering, cauterization, moxibustion, and bloodletting in the auricle. For 2500 years, people have employed auricular therapy for treating diseases, but the methods have been limited to bloodletting and cauterization. Only after 1957, the international scientific community became aware that the map of the ear resembles an inverted fetus, its introduction has led to auricular acupuncture (AA) becoming a more systemic approach, and, following the identification and standardization of more precise points, AA has been employed in clinical applications. The mechanisms of AA are considered to have a close relationship with the autonomic nervous system, the neuroendocrine system, neuroimmunological factors, neuroinflammation, and neural reflex, as well as antioxidation. Auricular therapy has been applied, for example, for pain relief, for the treatment of epilepsy, anxiety, and obesity, and for improving sleep quality. However, the mechanisms and evidence for auricular therapy warrant further study.

Acupoint Stimulation on Weight Reduction for Obesity: A Randomized Sham-Controlled Study

Auricular acupoint stimulation has become a popular weight loss method. However, its efficacy for obesity treatment has not been fully studied. This study aimed to investigate the effect of a 10-week intervention of auricular electrical stimulation combined with auricular acupressure on weight reduction in obese outpatients. In this single-blind randomized sham-controlled study, 134 participants were randomly assigned to an experimental group receiving stimulation at true acupoints, or a sham group receiving stimulation delivered in the same manner but at sham acupoints. Each participant received nutrition counseling by a nutritionist weekly. The results showed significant differences in body mass index, blood pressure, total cholesterol, triglyceride, and leptin or adiponectin over time within the group, but not between the groups. This study could not exclude the effect of placebo and dietary consultation. Further study that adds a control group receiving no treatment is therefore needed to confirm the effects of auricular acupressure.

Sham control methods used in ear-acupuncture/ear-acupressure randomized controlled trials: a systematic review

Ear-acupuncture/ear-acupressure (EAP) has been used for a range of health conditions with numerous randomized controlled trials (RCTs) investigating its efficacy and safety. However, the design of sham interventions in these RCTs varied significantly. This study systematically reviewed RCTs on EAP for all clinical conditions involving a number of sham EAPs as a control intervention. The review is guided by the Cochrane Handbook for Systematic Reviews of Interventions 5.1.0 and investigated the types and differences of sham EAP interventions. Four electronic English databases (The Cochrane Library, PubMed, Embase, CINAHL®) and two Chinese databases (CQVIP, CNKI) were searched in December 2012 and 55 published RCTs comparing real and sham EAP for any clinical condition were included. Characteristics of participants, real and sham interventions, and outcomes were extracted. Four types of sham methods were identified. Among the 55 RCTs, 25 studies involved treatment on nonspecific ear acupoints as the sham method; seven studies used nonacupoints on the ear; nine studies selected placebo needles or placebo ear-acupressure on the same ear acupoints for the real treatment; 10 studies employed pseudo-intervention; and five studies combined two of the above methods to be the sham control. Other factors of treatment such as number of points, treatment duration, and frequency also varied greatly. Risk of bias assessment suggests that 32 RCTs were "high risk" in terms of participants blinding, and 45 RCTs were "high risk" in terms of personnel blinding. Meta-analysis was not conducted due to the high clinical heterogeneity across included studies. No relationship was found between the sham designs and efficacy outcomes, or between the sham types and dropout rate. No solid conclusion of which design is the most appropriate sham control of EAP could be drawn in this review.

Effects of auricular acupressure using Sinapsis alba seeds on obesity and self-efficacy in female college students

OBJECTIVES

To examine the effects of auricular acupressure with Sinapsis alba seeds on obesity and self-efficacy.

DESIGN

Randomized controlled trial.

SETTINGS

College settings located in metropolitan areas of Korea.

PARTICIPANTS

A total of 49 female college students who were overweight or obese (body-mass index [BMI] ≥25.0 kg/m(2)) were recruited and randomly assigned to the experimental group (n=25) or the control group (n=24).

INTERVENTIONS

The experimental group applied three S. alba seeds to each of five auricular points (Shenmen, mouth, stomach, endocrine, and small intestine points). These participants were asked to stimulate those points 10 times at a rate of two times per second 30 minutes before mealtime, three times daily, for 1 month. They performed the procedure for each earlobe for alternating weeks (a total of 2 weeks' treatment for each ear).

OUTCOME MEASURES

The obesity index included weight (kg), BMI (kg/m(2)), percentage body fat, and waist-to-hip ratio. Self-efficacy was measured by using a self-efficacy scale.

RESULTS

Female students in the experimental group showed significant decreases in weight (t=10.76; p<0.001) and BMI (t=9.60; p<0.001) and significant improvement in self-efficacy (t=1.85; p<0.05) compared with those in the control group. However, percentage body fat (t=1.27; p>0.05) and waist-to-hip ratio (t=0.60; p>0.05) changes did not significantly differ between the two groups.

CONCLUSIONS

These findings suggest that auricular acupressure using S. alba seeds may be an effective intervention for decreasing weight and BMI and increasing self-efficacy of overweight and obese individuals.

Weight reduction effects of acupuncture for obese women with or without perimenopausal syndrome: a pilot observational study

This study was designed to compare the weight reduction effects of acupuncture for obese women with or without perimenopausal syndrome. We observed 60 women with either simple obesity or perimenopausal obesity (obesity complicated with perimenopausal syndrome) treated by five acupuncture treatments given in the first week of three successive four-week treatment courses, and obesity indexes including body weight, body mass index, obesity degree and waist/hip ratio were evaluated. Versus baseline, the obesity indexes decreased at the end of each treatment course in women with simple obesity (p < 0.05 or p < 0.01), while women with perimenopausal obesity showed no decrease at the end of the first course of treatment, and these indexes decreased at the end of the second and the third courses of treatment (p < 0.05). There was no difference when comparing obesity indexes recorded at the end of three courses of treatment and at the end of three-month follow-up between women with simple obesity and those with perimenopausal obesity. The results suggest that acupuncture reduced body weight in the obese women, and the weight loss occurred earlier in the treatment process for simple obesity than perimenopausal obesity.

Acupuncture in the treatment of obesity: a narrative review of the literature

Obesity is one of the leading health risk factors worldwide and is associated with several other risk factors and health problems including type 2 diabetes mellitus, cardiovascular disease and malignancies. Current conventional therapeutic strategies for obesity cannot achieve adequate weight control in all patients, so complementary types of treatment are also performed. Acupuncture, one of the oldest healing practices, represents the most rapidly growing complementary therapy which is recognised by both the National Institutes of Health and the WHO. A previous review concluded that acupuncture was superior to lifestyle advice, to sham acupuncture and to conventional medication. In this narrative review, the possible mechanisms of actions and the results of recent experimental and clinical studies with different forms of acupuncture (eg, body, auricular, manual and electroacupuncture) are presented. In particular, the effects of acupuncture on anorexigenic and orexigenic peptides, insulin resistance, lipid metabolism and inflammatory markers are discussed. Both experimental and clinical current data suggest that acupuncture exerts beneficial effects on the mechanisms of obesity. Some data suggest that electroacupuncture may be more effective than manual acupuncture; however, the most effective frequency remains controversial. Combination of different forms of acupuncture with diet and exercise seems to be necessary for achieving and maintaining weight loss.  Further prospective clinical trials are needed to establish the effectiveness of this complementary method for obesity treatment.

Effects of auricular acupressure on body weight parameters in patients with chronic schizophrenia

Auricular acupressure is widely used in complementary and alternative medicine to reduce body weight, but little is known about the effects of auricular acupressure on body weight parameters in patients with chronic schizophrenia. The purpose of this study was to evaluate the effects of auricular acupressure on body weight parameters in patients with chronic schizophrenia. Eighty-six inpatients with schizophrenia were recruited from chronic wards in a psychiatric center. The participants were randomly divided into experimental (acupressure at 4 acupuncture sites: hunger, stomach, shenmen and endocrine) and control groups, and body weight parameters were determined weekly for 8 weeks. There was no significant difference between the experimental and control groups in mean body weight, waist circumference, or body fat percentage at the pretest or during the entire 8-week study period. Therefore, auricular acupressure did not cause body weight reduction in patients with chronic schizophrenia.

Variations of Brain Activities of Acupuncture to TE5 of Left Hand in Normal Subjects

This paper presents the evident effects of acupoint stimulation, using EEG (electroencephalogram) measurements. With acupuncture stimulation and the EEG measurement on the same meridian, EEG is able to accurately detect the effects of acupunctural point stimulation on brain waves.

In this study, 24 subjects without heart or neural diseases were randomly separated into two groups of 12, named test and control groups. Similar procedures are performed; the subjects lay on a bed with eyes closed for ten minutes as the baseline. The test group received acupuncture at their Waiguan points (TE5) on their left hands for 20 minutes, while the control group did not. EEGs are recorded during pre-acupuncture, acupuncture stimulation and post-acupuncture stimulation periods. The EEG electrodes are at the T3, T4, O1 and O2 locations. Continuous wavelet transformation analysis is adopted; therefore, EEGs are divided into the following bands: δ (0.5–4HZ), θ (4–8HZ), α (8–13HZ) and β (13–30HZ).

During acupuncture stimulation, the θ energy is increased and had statistical differences at all electrode points, T3, T4, O1 and O2. Upon removing the needle, the energy at the T3 and T4 points slowly declined and revealed obvious statistical differences. During acupuncture, only α energy has been noted to have statistical difference and it was increased at the T3 point. However, the energy was decreased and had no statistical difference after five minutes.

Acupuncture is proven to be able to affect brain waves, as the stimulation might have changed the tissues between the cranium and scalp; therefore, the brain waves are detected more easily.

Auricular Acupuncture May Suppress Epileptic Seizures via Activating the Parasympathetic Nervous System: A Hypothesis Based on Innovative Methods

Auricular acupuncture is a diagnostic and treatment system based on normalizing the body's dysfunction. An increasing number of studies have demonstrated that auricular acupuncture has a significant effect on inducing parasympathetic tone. Epilepsy is a neurological disorder consisting of recurrent seizures resulting from excessive, uncontrolled electrical activity in the brain. Autonomic imbalance demonstrating an increased sympathetic activity and a reduced parasympathetic activation is involved in the development and progress of epileptic seizures. Activation of the parasympathetic nervous system such as vagus nerve stimulation has been used for the treatment of intractable epilepsy. Here, we propose that auricular acupuncture may suppress epileptic seizures via activating the parasympathetic nervous system.

Episodes of injuries and frequent usage of traditional Chinese medicine for Taiwanese elite wrestling athletes

Wrestling normally places extreme demands on the body and thus may cause various kinds of injuries. An in-depth understanding of the episodes of injured sites, types, timings, and treatment modalities would help participants be aware of wrestling-related injury occurrences so as to develop effective preventive measures. Therefore, this study aims to investigate the gender-specific injuries among elite wrestling athletes. Subjects were selected from the 2009 Taiwanese National Wrestling Sport Championship. Participants were adolescent wrestling athletes, ages 16-18, who must have received at least one bronze medal at national level tournaments in 2008. A total of 118 respondents, 96 males and 22 females, completed and returned the questionnaire in which demographic data and information about the types, sites, and timings of injuries suffered and treatment modalities adopted were elicited. The data were analyzed with independent t-tests. The questionnaire results revealed a significantly higher injury rate for males than for females. The top three injured sites for males were waist (11.1%), ankle joint (10.1%) and finger (9.6%); while for females were ankle joint (13.6%), knee (12.5%) and waist (11.3%). Contusions were the most frequent type of injury: for males (73.5%) and for females (70.6%); followed by tendon inflammation for males (10.7%) and accumulated injuries for females (15.2%). During training and matching periods, the frequency of injuries for males (69.0%) is lower than that for females (81.8%). Traditional Chinese medicine (TCM) with acupuncture and moxibustion was the most common treatment modalities used for males (51.8%) and for females (68.0%); followed by orthopedics: for males (29.5%) and for females (18.0%). The present study contributed as the first effort to reveal the potency of using TCM with acupuncture and moxibustion in wrestling competitions. To prevent possible brain and body injuries in wrestling, safety education, skills and rules, and scoring systems may require further revision. Increased training of wrestling health professionals and advanced research and development of auxiliary training devices and protective equipment for wrestling athletes are also recommended.