WB-EMS Combined With Nutritional Guidance for a High-Protein Diet on Body Composition, Muscle Function, Psychological and Functional Outcomes in Older Adults With Excess Adiposity

This is a 16-week, parallel-group, outcome-assessor-blinded randomized clinical trial (RCT), approved by the UniCesumar Ethics Committee (Opinion No. 8.718.082 / CAAE: 01410126.9.0000.5539). The study aims to investigate the effects of resistance training combined with whole-body neuromuscular electrical stimulation (WB-NMES) and nutritional guidance focused on a high-protein diet on body composition, anthropometric parameters, and quality of life in older adults with overweight and obesity residing in Maringá-PR, Brazil.

The sample will consist of 36 older adults of both sexes (age $\\ge$ 60 years, BMI $\\ge$ 25 $kg/m\^2$, and physically inactive), randomly allocated (stratified randomization by sex in a 1:1:1:1 ratio) into four experimental groups (n = 9 per group):

RT + NOR: conventional resistance training combined with normoprotein diet guidance;

RT + PRO: conventional resistance training combined with high-protein diet guidance;

WB-NMES + RT + NOR: resistance training using WB-NMES combined with normoprotein diet guidance;

WB-NMES + RT + PRO: resistance training using WB-NMES combined with high-protein diet guidance.

Training Protocol and Electrical Stimulation: The exercise interventions will take place twice a week (sessions of approximately 25 minutes) over 16 weeks, under the supervision of qualified professionals. Participants will perform seven exercises (leg curl, leg extension, kettlebell squat, lat pulldown, seated machine row, incline bench press, and crunch on a bench), executing 2 sets of 1 minute per exercise, with a 45-second rest interval. Training intensity will be progressive and monitored by the OMNI Rating of Perceived Exertion Scale (OMNI-RPE: 2-3 in Phase 1 up to 7-8 in Phase 4, with a gradual load reduction phase in the 16th week).

In the WB-NMES groups, the exercise will be simultaneously combined with electrical current applied through a suit with integrated electrodes (frequency of 85 Hz, pulse width of 400 $\\mu$s, duty cycle of 5 s on/5 s off, and a ramp-up time of 0 s). Intensity adjustments will be limited to a maximum of 5 points on the Visual Analog Scale for pain/discomfort (VAS 0-10). All participants will undergo prior familiarization sessions.

Nutritional Intervention: This will be conducted through a hybrid approach (individualized face-to-face sessions and remote monitoring via a WhatsApp group), prioritizing contextualized nutritional education. In the high-protein intake groups, the consumption goal will be 1.2 to 1.5 g of protein/kg/day, distributed evenly across meals. In the normoprotein (control) groups, the guidance will focus on general principles of healthy eating and hydration, without encouraging an increase in protein intake.

Assessments and Outcomes: Assessments will be performed at baseline (T0) and after 16 weeks (T16).

Body Composition: Assessed using multi-frequency bioelectrical impedance analysis (InBody 570) under a strict preparation protocol (lean mass, skeletal muscle mass, total and visceral body fat, body water), with reproducibility verified on two distinct days at T0.

Anthropometry: Circumferences (neck, waist, abdomen, hip, thigh, and calf) measured in duplicate by a blinded evaluator, following ISAK guidelines.

Physical and Functional Performance Assessment:

Maximal Isometric Strength (Upper Limbs): Assessed by handgrip dynamometry (Jamar®), following ASHT guidelines. The participant will perform three attempts with each hand, sitting in a standardized posture, with a 60-second rest interval. The highest value (kgf) of the dominant hand will be considered for analysis.

Localized Muscular Endurance (Senior Fitness Test):

Lower Limbs: 30-second chair stand test (maximum full repetitions in a standardized chair).

Upper Limbs: 30-second arm curl test. Using a 2 kg (women) and 4 kg (men) dumbbell, the maximum number of correct repetitions with the dominant arm will be recorded.

Muscular Power (Upper Limbs): Medicine ball throw (2 kg). The participant, seated and without feet touching the floor, will throw the ball forward explosively. Three attempts will be made (60s interval), considering the longest distance achieved.

Aerobic Endurance: 6-minute walk test (6MWT) in a 30-meter corridor, following ATS guidelines. The total distance will be recorded, along with heart rate monitoring and perceived exertion (Borg Scale) pre- and post-test.

Functional Mobility and Fall Risk: Timed Up and Go (TUG) test. Will evaluate the time (in seconds) taken to rise from a chair, walk 3 meters, return, and sit down. Two attempts will be performed, considering the shortest time.

Self-Reported Functional Capacity: Self-reported functional disability will be measured with the World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) (36-item version), developed by the WHO, assessing difficulties in the last 30 days across six domains. Responses range on a five-point Likert scale, and the scores, calculated by simple sum, are converted to a 0 to 100 scale, where higher scores reflect greater disability. The instrument will be applied self-administered or by interview to complement objective physical data with the participants' own perception of the impact of each intervention.

Psychosocial, Motivational, and Adherence Assessments:

Basic Psychological Needs: Satisfaction in the exercise context will be assessed by the Brazilian version of the Basic Psychological Needs in Exercise Scale (BPNES) (12 items, 5-point Likert scale). The instrument covers three subscales: Autonomy, Competence, and Relatedness. Higher mean scores indicate greater satisfaction of the respective psychological need.

Motivational Regulation: Will be measured by the Brazilian version of the Behavioral Regulation in Exercise Questionnaire (BREQ-3) (23 items, 5-point Likert scale), which assesses six forms of behavioral regulation (from amotivation to intrinsic motivation). From the results, the Relative Autonomy Index (RAI) will be calculated, in which more positive values reflect a more autonomous motivational profile.

Program Adherence: Quantified by the participants' relative attendance at supervised sessions (sessions attended / scheduled sessions $\\times$ 100%), with a minimum target set at 75%.

Quality of Life: Assessed using the World Health Organization Quality of Life - Old (WHOQOL-OLD) questionnaire, developed by the WHO specifically for older adults. The instrument consists of 24 questions (5-point Likert scale) distributed across six facets: Sensory Abilities; Autonomy; Past, Present and Future Activities; Social Participation; Death and Dying; and Intimacy. The questionnaire will be applied individually by trained researchers. Scores will be converted to a standardized 0 to 100 scale, where higher scores indicate a better perception of quality of life.

Statistical Analysis: Analyses will follow the intention-to-treat (ITT) principle, using Linear Mixed Models for Repeated Measures (fixed factors: Group and Time; random factor: Participants), followed by Tukey's post-hoc test (significance level set at $p < 0.05$).

• Whole-Body Neuromuscular Electrical Stimulation (WB-NMES) (Device), also known as Whole-Body Electromyostimulation: 16-week intervention, 2 sessions/week (\~25 min each). Exercises performed: leg curl, leg extension, kettlebell squat, lat pulldown, machine row, incline chest press, bench crunch. Simultaneous electrical stimulation via impulse suit: 85 Hz frequency, 400 µs pulse width, 5s ON / 5s OFF duty cycle, 0s ramp-up. Intensity adjusted progressively using OMNI-RPE scale and capped at VAS 5 for discomfort.
• Conventional Resistance Training (Behavioral), also known as Resistance Exercise, RT: 16-week resistance training intervention without electrical stimulation, 2 sessions/week (\~25 min each). Participants perform the same 7 exercises (leg curl, leg extension, kettlebell squat, lat pulldown, machine row, incline chest press, bench crunch) with 2 sets of 1 min and 45s rest. Progression managed via OMNI-RPE scale (RPE 2-3 progressing to 7-8).
• High-Protein Nutritional Guidance (Behavioral), also known as High-Protein Diet: Hybrid nutritional intervention (individualized in-person sessions and remote WhatsApp follow-ups). Guidance aims to achieve a daily protein intake of 1.2 to 1.5 g/kg/day, evenly distributed across main meals throughout the day.
• Normoproteic Nutritional Guidance (Behavioral), also known as Control Diet Guidance, Standard Healthy Eating Guidance: Hybrid nutritional guidance focusing on general principles of healthy eating, food choices, and hydration according to national dietary guidelines, without targeting or encouraging increased protein intake.

Primary outcomes

• Change in Fat-Free Mass [The duration of the entire program will be approximately one year, from registration through to tabulation and writing.]: Change in fat-free mass (in kg) from baseline to the end of the 16-week intervention, assessed using the body composition assessment method specified in the study protocol.
• Change in Skeletal Muscle Mass [The duration of the entire program will be approximately one year, from registration through to tabulation and writing.]: Change in skeletal muscle mass (in kg) from baseline to the end of the 16-week intervention, assessed using the body composition assessment method specified in the study protocol.
• Handgrip Strength (HGS) [Baseline (week 0) and post-16 weeks of intervention.]: Assessed by hydraulic hand dynamometry (Jamar®), measured in kilogram-force (kgf), to evaluate changes in upper-limb maximal muscle strength resulting from the interventions.

Secondary outcomes

• Knee Extension and Flexion Peak Torque [Baseline (week 0) and post-16 weeks of intervention.]: Measured using an isokinetic dynamometer (Biodex System 4 Pro) in Newton-meters (N·m) at angular velocities of 60°/s (peak torque) and 180°/s (muscle power).
• Distance in Medicine Ball Throw Test [Baseline (week 0) and post-16 weeks of intervention.]: Distance achieved (in meters) throwing a 2 kg medicine ball from the chest, assessing upper-body rapid force and muscle power.
• 30-Second Chair Stand Test [Baseline (week 0) and post-16 weeks of intervention.]: Total number of full repetitions of sitting and standing from a standard chair completed within 30 seconds (30-second Chair Stand Test).
• 30-Second Arm Curl Test [Baseline (week 0) and post-16 weeks of intervention.]: Total number of arm curl repetitions executed in 30 seconds using a standardized weight (Arm Curl Test).
• Time in Timed Up and Go (TUG) Test [Baseline (week 0) and post-16 weeks of intervention.]: Time in seconds required to stand up from a chair, walk 3 meters, turn, walk back, and sit down again.
• WHODAS 2.0 Functional Disability Score [Baseline (week 0) and post-16 weeks of intervention.]: Global score of the World Health Organization Disability Assessment Schedule 2.0 (36-item version), measuring the level of limitation in daily activities. The score ranges from 0 to 100, with higher scores indicating greater disability and worse functioning.
• Relative Body Fat [Baseline (week 0) and post-16 weeks of intervention.]: Percentage of body fat (%) determined by multi-frequency bioelectrical impedance analysis (InBody 570).
• Body Girths (Waist, Abdomen, Hip, Thigh, and Calf) [Baseline (week 0) and post-16 weeks of intervention.]: Anthropometric measurements in centimeters (cm) following ISAK standards (neck, waist, abdomen, hip, medial thigh, and calf).
• Lipid Panel and Apolipoproteins [Baseline (week 0) and post-16 weeks of intervention.]: Plasma levels in mg/dL of total cholesterol, HDL-c, LDL-c, VLDL-c, triglycerides, and apolipoproteins measured in fasting blood samples.
• Inflammatory Cytokines (IL-6 and IL-1beta) [Baseline (week 0) and post-16 weeks of intervention.]: Plasma concentrations of Interleukin-6 (IL-6) and Interleukin-1beta (IL-1beta), expressed in pg/mL.
• Gastrointestinal Gut Peptides and Leptin [Baseline (week 0) and post-16 weeks of intervention]: Fasting plasma concentrations of appetite-regulating hormones, including Glucagon-Like Peptide-1 (GLP-1), Peptide YY (PYY), Gastrin, and Leptin, all expressed in pg/mL.
• Plasma BDNF Concentration [Baseline (week 0) and post-16 weeks of intervention.]: Plasma concentration of Brain-Derived Neurotrophic Factor (BDNF), expressed in picograms per milliliter (pg/mL).
• Finger-Toe Pulse Wave Velocity (PWV) [Baseline (week 0) and post-16 weeks of intervention.]: Pulse Wave Velocity, assessment via applanation tonometry to estimate arterial stiffness, expressed in meters per second (m/s).
• Binge Eating [Baseline (week 0) and post-16 weeks of intervention.]: Binge eating will be estimated from the Binge Eating Scale (BES), adapted from the University of Rhode Island Change Assessment (URICA). URICA ranges from 0-46 points, with higher scores indicating greater binge eating severity.
• Basic Psychological Needs in Exercise [Baseline (week 0) and post-16 weeks of intervention]: Basic Psychological Needs will be monitored through the Basic Psychological Needs in Exercise Scale (BPNES). The BPNES ranges from 18-90 points, with higher scores indicating greater satisfaction of basic psychological needs in exercise.
• Motivational Regulation [Baseline (week 0) and post-16 weeks of intervention]: The motivational regulation will be assessed through the Behavioral Regulation in Exercise Questionnaire-3 (BREQ-3). The BREQ-3 assesses six motivational regulations, each scored from 0-4.
• Fasting glucose [Baseline (week 0) and post-16 weeks of intervention.]: Fasting blood glucose concentration, measured in milligrams per deciliter (mg/dL).
• Fasting insulin [Baseline (week 0) and post-16 weeks of intervention.]: Fasting blood insulin concentration, measured in microinternational units per milliliter (µIU/mL).
• C-peptide [Baseline (week 0) and post-16 weeks of intervention.]: Fasting blood C-peptide concentration, measured in nanograms per milliliter (ng/mL).
• Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) [Baseline (week 0) and post-16 weeks of intervention.]: Insulin resistance will be estimated using the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) index, calculated from fasting blood glucose and fasting insulin concentrations. HOMA-IR is a dimensionless index, with higher values indicating greater insulin resistance.
• Geriatric Depression Scale-15 (GDS-15) Total Score [Baseline (week 0) and post-16 weeks of intervention.]: Total score on the Geriatric Depression Scale-15 (GDS-15), a 15-item screening scale for depressive symptoms in older adults. Scores range from 0 to 15, with higher scores indicating greater severity of depressive symptoms.
• Beck Depression Inventory-II (BDI-II) Total Score [Baseline (week 0) and post-16 weeks of intervention.]: Total score on the Beck Depression Inventory-II (BDI-II), a 21-item self-report measure of depressive symptoms. Scores range from 0 to 63, with higher scores indicating greater severity of depressive symptoms.
• Generalized Anxiety Disorder-7 (GAD-7) Total Score [Baseline (week 0) and post-16 weeks of intervention.]: Total score on the Generalized Anxiety Disorder-7 (GAD-7), a 7-item self-report scale assessing symptoms of generalized anxiety. Scores range from 0 to 21, with higher scores indicating greater severity of anxiety symptoms.
• World Health Organization Quality of Life-OLD (WHOQOL-OLD) Total Score [Baseline (week 0) and post-16 weeks of intervention.]: Total score of the World Health Organization Quality of Life-OLD (WHOQOL-OLD), an instrument designed to assess quality of life in older adults. Scores range from 0 to 100, with higher scores indicating better quality of life.
• Pittsburgh Sleep Quality Index (PSQI) Global Score [Baseline (week 0) and post-16 weeks of intervention.]: Global score of the Pittsburgh Sleep Quality Index (PSQI), a self-report instrument assessing sleep quality and sleep disturbances. Scores range from 0 to 21, with higher scores indicating worse sleep quality.
• Appraisal of Self-Care Agency Scale (ASA-A) Total Score [Baseline (week 0) and post-16 weeks of intervention.]: Total score of the Appraisal of Self-Care Agency Scale (ASA-A), assessing an individual's self-care agency. Scores range from 24 to 120, with higher scores indicating greater self-care agency.

Other outcomes

• Body Water Distribution via Bioelectrical Impedance [Baseline (week 0) and post-16 weeks of intervention.]: Mapping of total body water (TBW), intracellular water (ICW), and extracellular water (ECW) volumes, in liters, via bioelectrical impedance analysis (InBody 570) for hydration status monitoring.
• Participant-reported experience and acceptability of the intervention (qualitative) [At the end of the 16-week intervention (post-intervention)]: Qualitative exploration of participants' experience of the 16-week intervention. Completers from all four factorial arms are invited to an individual semi-structured interview (audio-recorded, \~20-30 min) by trained interviewers not involved in delivering the sessions; modality-specific blocks (WB-EMS and nutritional guidance) are administered according to each participant's allocation, allowing contrasts across arms. Interviews are transcribed verbatim and analysed using reflexive thematic analysis (Braun \& Clarke), with a primarily deductive orientation around predefined domains: experience and acceptability of the interventions (resistance training, WB-EMS, nutritional guidance); health promotion and empowerment; and the three basic psychological needs of Self-Determination Theory (autonomy, competence, relatedness), while remaining open to additional themes. As a qualitative outcome, results are reported as constructed themes rather than a numeric metric. Conduct and reporting fol

Sex: All, ages: 60 Years to any

Inclusion Criteria:

* Age 60 years or older (both sexes);
* Body Mass Index (BMI) ≥ 25 kg/m² (overweight or obese);
* Physically inactive (not engaged in regular structured exercise for at least 6 months prior to the study);
* Medical clearance to engage in progressive resistance exercise and neuromuscular electrical stimulation.

Exclusion Criteria:

* Presence of electronic implants (e.g., cardiac pacemakers, defibrillators) or metallic implants that contraindicate WB-NMES;
* Absolute contraindications to WB-NMES (e.g., active neoplasia, severe epilepsy, acute inflammatory diseases, severe cardiac arrhythmias, thrombosis);
* Severe cognitive impairment that prevents understanding instructions or questionnaires;
* Disabling musculoskeletal or neurological disorders that hinder exercise performance;
* Uncontrolled chronic diseases (e.g., uncontrolled hypertension or diabetes);
* Current use of medications or supplements known to significantly affect protein metabolism or muscle mass;
* Adherence below 85% in training sessions or nutritional follow-ups during the study period.

• Vitor S Painelli, Dr., Principal investigator, UniCesumar - Centro Universitário Cesumar