Overweight and obesity are escalating global health concerns, impacting over 2.1 billion people worldwide. This condition significantly elevates the risk of various health complications, including hypertension, metabolic disorders, type 2 diabetes, cardiovascular diseases, and certain cancers. The economic burden of treating these secondary diseases and the increased risk of work disability place a substantial strain on healthcare systems.
The Challenge of Weight Loss
Effective weight loss strategies aim to reduce body fat while preserving muscle mass, which is crucial for maintaining a healthy metabolism. Traditional approaches, such as energy restriction, often lead to the loss of lean body mass, negating some of the health benefits. Creating a negative energy balance through calorie restriction alone can result in a loss of lean body mass of up to one-third of the total weight loss.
The Role of Physical Activity
Increased physical activity, including endurance and resistance exercise, contributes to a negative energy balance and promotes fat loss. Intense resistance exercise boosts energy demands for up to 72 hours post-exercise and increases resting metabolic rate (RMR). However, time constraints, orthopedic issues, and aversion to strenuous exercise can hinder participation in conventional exercise programs.
Whole-Body Electromyostimulation (WB-EMS): A Promising Alternative
Whole-body electromyostimulation (WB-EMS) emerges as a time-efficient, joint-friendly, and customizable training technology, making it suitable for individuals with limited time or exercise intolerance. Studies suggest that WB-EMS can achieve similar hypertrophic effects, muscle strength gains, and fat loss as high-intensity resistance training.
WB-EMS and Lean Body Mass
One study investigated the effects of WB-EMS on lean body mass (LBM) in overweight women. Ninety premenopausal women aged 25-50 were divided into three groups:
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- CG (Control Group): Negative energy balance (-500 kcal/day) through energy restriction with compensatory protein intake (1.2 g/kg body mass/day).
- PA (Physical Activity Group): Negative energy balance (-500 kcal/day) through energy restriction (-250 kcal/day) and increased physical activity (-250 kcal/day) with increased protein intake (1.7 g/kg body mass/day).
- WB-EMS Group: Negative energy balance (-500 kcal/day) through energy restriction and increased physical activity with increased protein intake plus WB-EMS.
The intervention lasted 16 weeks, with WB-EMS applied 1.5 times per week for 20 minutes (85 Hz; 350 μs; intermittent 6-second impulse, 4-second rest).
Results indicated that LBM decreased in the CG (-113 ± 1,872 g) and PA groups (-391 ± 1,832 g), while it increased in the WB-EMS group (387 ± 1,769 g). Although changes were not statistically significant overall (p > 0.05), pairwise comparisons revealed significant differences between WB-EMS and PA (p = 0.049).
Study Design and Methodology
The Weight-Reduction and Electromyostimulation Plus Protein (WREPP) project, a randomized controlled trial (RCT), was conducted by the Institute of Medical Physics (IMP) at Friedrich-Alexander University Erlangen-Nuremberg (FAU). The study adhered to the Helsinki Declaration and was approved by the FAU Ethics Committee.
Participants were recruited from the Erlangen-Nuremberg area and screened based on specific eligibility criteria, including age, premenopausal status, absence of relevant diseases, and body fat rate > 28%. Participants were randomly assigned to the three intervention groups, stratified by body fat rate.
Nutritional analysis and consultations guided participants in achieving a 500 kcal/day energy reduction through carbohydrate restriction. Protein supplementation ensured a daily intake of 1.2 g/kg body mass/day in the CG and 1.7 g/kg body mass/day in the PA and WB-EMS groups.
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The PA group increased daily activity to expend an additional 250 kcal/day, monitored by fitness trackers. The WB-EMS group received WB-EMS training 1.5 times per week for 20 minutes, targeting eight muscle groups with supervised sessions.
Body composition, including LBM, was assessed using bio-impedance analysis (BIA). Statistical analysis included intention-to-treat analysis with multiple imputation for missing values.
Novel Approaches: Correlated Vagus Nerve Stimulation (VNS)
Recent advancements in neuromodulation offer potential therapeutic interventions for weight control. Vagus nerve stimulation (VNS) has shown promise in influencing food intake, energy metabolism, and glycemic control, leading to weight loss.
Development of a Correlated VNS System
Researchers have developed a correlated VNS system that is battery-free and automatically generates electrical stimulations in response to stomach movement. A flexible nanogenerator device attached to the stomach surface produces biphasic electrical pulses during peristalsis, stimulating vagal afferent fibers to reduce food intake.
Working Principle and Biocompatibility
The VNS device consists of triboelectric layers that generate voltage signals based on stomach motion. As the stomach distends and contracts, the triboelectric layers come into contact and separate, driving electrons through connections with the vagus nerve.
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The device is packaged with biocompatible materials, including polyimide, polydimethylsiloxane (PDMS), and ecoflex, to ensure mechanical robustness and prevent erosion in the physiological environment. Biocompatibility tests with mouse fibroblast 3T3 cells confirmed that the encapsulated device is non-cytotoxic.
Functionality and Stability
Voltage signals measured from the VNS device implanted in rats exhibited similar amplitudes to those measured in vitro. Higher voltage outputs were recorded at higher frequencies of stomach deformation. The device demonstrated good stability and durability in the biological environment over several weeks.
Electrophysiological signals confirmed that the VNS device effectively stimulated the vagus nerves. The amplitude and number of electric pulses per signal group increased when the device was activated.
In Vivo Studies and Weight Loss Results
In vivo studies on rats demonstrated the effectiveness of the correlated VNS system in achieving weight loss. Rats with the VNS device implanted on their stomachs experienced a 38% weight loss in 15 days without further rebound. Small animal computed tomography (CT) imaging confirmed the stability of the implanted device over 12 weeks.
Hematology data indicated the biosafety of the implanted VNS device, with no significant differences observed in blood glucose levels, infection-related lymphocytes, or hematopoietic function-related red blood cells.
Comparison with Electrical Muscle Stimulation (EMS)
Another study evaluated the effects of electrical muscle stimulation (EMS) on abdominal obesity. Participants were treated with EMS or transcutaneous electrical nerve stimulation (TENS) for 12 weeks. The EMS group achieved a significantly greater decrease in waist circumference compared to the TENS group (5.2±2.8 cm vs. 2.9±3.3 cm, P=0.005).
Fasting free fatty acid (FFA) levels were significantly higher in the EMS group, suggesting that EMS induces lipolysis in intramuscular adipose tissue. However, no significant intergroup differences were found for abdominal fat distribution or other metabolic and biochemical characteristics.
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