Breath Acetone During Tirzepatide Treatment and Resistance Training in Adults With Obesity (RESIST-EXHALE)

Exhaled Breath Analysis for the Prediction of Treatment Response During Tirzepatide Therapy and Resistance Training in Adults With Obesity - An Ancillary Study to the RESIST Trial

This study is an ancillary study to the RESIST trial, in which adults with obesity receive the weight-loss medication tirzepatide and are randomly assigned to a structured resistance training program or to usual care for 24 weeks. RESIST-EXHALE measures acetone in exhaled breath, a non-invasive marker of fat burning, at all seven RESIST visits (Week 0 to Week 24). The study investigates how breath acetone changes during treatment, whether this change differs between participants with and without resistance training, and whether breath acetone at the start or early in treatment can predict the individual response to treatment, such as weight loss and preservation of muscle. The measurement takes about 15-20 minutes at the first visit and about 10 minutes at each later visit. No additional visits, interventions or biological samples are part of this ancillary study.

Study Overview

• Status: Not yet recruiting
• Conditions: Obesity (Disorder)
• Intervention / Treatment: Drug: Tirzepatide; Behavioral: Structured resistance training

Detailed Description

RESIST-EXHALE is a prospective, observational, monocentric ancillary study conducted at the TUM Klinikum, Munich, Germany. Active participation in the RESIST trial (protocol code RESIST-26-HAL-0150-I; EU CT number 2026-526200-69-00) is a prerequisite for enrolment. RESIST is a randomized, controlled, open-label Phase IV trial evaluating a structured resistance training program versus usual care in 150 adults with obesity treated with tirzepatide over 24 weeks.

RESIST-EXHALE involves no investigational medicinal product, no intervention and no randomization. Assignment to resistance training or usual care occurs exclusively within the RESIST trial. Breath acetone concentration is measured under standardized fasting conditions (at least 8 hours) at all RESIST visits (V1, Week 0; V2-V6, Weeks 4, 8, 12, 16, 20; V7, Week 24) using a handheld point-of-care breath acetone analyzer (Nutrion™, Alivion AG) with volume-controlled, end-tidal breath sampling. The device is used for research purposes only and does not inform clinical decisions. A short questionnaire on known confounders of breath acetone is completed before each measurement.

The primary endpoint is the change in breath acetone from V1 to V7, compared between arms. All analyses are exploratory and hypothesis-generating; no formal sample size calculation or multiplicity adjustment is performed.

• Study Type: Observational
• Enrollment (Estimated): 150

Contacts and Locations

• Study Contact: Name: Katharina Timper, Prof. Dr. med.; Phone Number: +49 89 289 24930; Email: Katharina.Timper@mri.tum.de
• Study Contact Backup: Name: Kristina Geyer, Dr. rer. nat.; Phone Number: +49 89 289 24925; Email: k.geyer@tum.de

Study Locations

• Germany
  • München, Germany, 80809
    • TUM Klinikum, Department for Clinical Nutritional Medicine and Department for Preventive Sports Medicine and Sports Cardiology, Am Olympiacampus 11, 80809 Munich, Germany
    • Contact: Katharina Timper, Prof. Dr. med.; Phone Number: +49 89 289 24930; Email: Katharina.Timper@mri.tum.de

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 60 years (Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

Participants of the RESIST trial at the TUM Klinikum, Munich: adults aged 18-60 years with obesity (BMI ≥ 30 kg/m²) without manifest type 2 diabetes or structural cardiovascular disease, eligible for pharmacological weight-loss therapy and suitable for a structured resistance training program. Sufficient command of German is required.

Description

Inclusion Criteria:

• Provisional eligibility for randomization into the RESIST trial (based on all RESIST screening assessments available at the time of informed consent for this ancillary study)
• Written informed consent for this ancillary study

Exclusion Criteria:

• Non-randomization into the RESIST trial for any reason
• Any anatomical or functional condition preventing breath sampling through a mouthpiece (e.g., tracheostomy, laryngectomy, severe facial deformity), such that a valid end-tidal breath sample cannot be obtained

Key eligibility criteria of the RESIST trial (for context only; full criteria see RESIST protocol RESIST-26-HAL-0150-I):

• Age 18-60 years
• Obesity (BMI ≥ 30 kg/m²)
• No manifest type 2 diabetes
• No structural cardiovascular disease
• Not pregnant or breastfeeding
• Sufficient command of the German language

Study Plan

How is the study designed?

Design Details

• Observational Models: COHORT
• Time Perspectives: PROSPECTIVE

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Resistance training + tirzepatide; RESIST participants randomized to the structured resistance training arm of the RESIST trial, receiving tirzepatide and individualized diet and physical activity counselling. Assignment occurs within RESIST, not within this ancillary study.	Drug: Tirzepatide; Once-weekly subcutaneous injection over 24 weeks, starting at 2.5 mg/week and increased by 2.5 mg every 4 weeks as tolerated up to a maximum of 10 mg/week, in accordance with the SmPC. Administered within the RESIST trial (not part of this ancillary study).; Behavioral: Structured resistance training; Machine-based structured resistance training over 24 weeks, delivered within the RESIST trial (not part of this ancillary study). Progressive program with an acclimation phase (weeks 1-4) and a target phase (weeks 5-24; 8-12 repetitions at approx. 70-75% 1-RM, with additional eccentric overload from week 9). Sessions are intended to be fully supervised during the first 6 weeks whenever feasible, thereafter at least one supervised session after each interim visit; remaining sessions at the trial site or at partner fitness facilities.
Usual care + tirzepatide; RESIST participants randomized to the usual care arm of the RESIST trial, receiving tirzepatide and individualized diet and physical activity counselling. Assignment occurs within RESIST, not within this ancillary study.	Drug: Tirzepatide; Once-weekly subcutaneous injection over 24 weeks, starting at 2.5 mg/week and increased by 2.5 mg every 4 weeks as tolerated up to a maximum of 10 mg/week, in accordance with the SmPC. Administered within the RESIST trial (not part of this ancillary study).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in breath acetone concentration from baseline to end of treatment	Breath acetone concentration (ppm) measured under standardized fasting conditions with a handheld point-of-care breath acetone analyzer. Change from baseline to Week 24, compared between the resistance training group and the usual care group, adjusted for baseline.	Baseline (Week 0) and end of treatment (Week 24)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Baseline breath acetone and change in body weight	Regression coefficient of the percentage change in body weight (%; calibrated scale) on baseline breath acetone (ppm; handheld breath acetone analyzer)	Baseline (Week 0) to Week 24
Baseline breath acetone and change in fat mass	Regression coefficient of the change in fat mass (kg; bioelectrical impedance analysis) on baseline breath acetone (ppm; handheld breath acetone analyzer)	Baseline (Week 0) to Week 24
Baseline breath acetone and change in skeletal muscle mass	Regression coefficient of the change in skeletal muscle mass (kg; bioelectrical impedance analysis) on baseline breath acetone (ppm; handheld breath acetone analyzer)	Baseline (Week 0) to Week 24
Baseline breath acetone and change in thigh muscle volume	Regression coefficient of the change in contractile thigh muscle volume (mL; MRI) on baseline breath acetone (ppm; handheld breath acetone analyzer)	Baseline (Week 0) to Week 24
Baseline breath acetone and change in knee extension strength	Regression coefficient of the change in peak isometric knee extension torque (Nm; isokinetic dynamometer) on baseline breath acetone (ppm; handheld breath acetone analyzer)	Baseline (Week 0) to Week 24
Change in breath acetone concentration from baseline to Week 4	Breath acetone concentration (ppm; handheld breath acetone analyzer) under standardized fasting conditions; change from Week 0 to Week 4, compared between groups	Baseline (Week 0) and Week 4
Time course of breath acetone concentration during treatment	Breath acetone concentration (ppm; handheld breath acetone analyzer) at Weeks 0, 4, 8, 12, 16, 20 and 24, compared between groups	Week 0 to Week 24
Predictive value of early change versus baseline breath acetone for clinical response	Comparative predictive value of the change in breath acetone concentration from Week 0 to Week 4 versus the baseline (Week 0) breath acetone concentration alone (ppm; handheld breath acetone analyzer) for the percentage change in body weight (%; calibrated scale) from Week 0 to Week 24 (RESIST data).	Baseline (Week 0) to Week 24
Baseline breath acetone and change in handgrip strength	Regression coefficient of the change in maximum handgrip strength (kg; hand dynamometer) on baseline breath acetone (ppm; handheld breath acetone analyzer)	Baseline (Week 0) to Week 24

Collaborators and Investigators

• Sponsor: Technical University of Munich

Study record dates

Study Major Dates

• Study Start (Estimated): October 22, 2026
• Primary Completion (Estimated): July 31, 2027
• Study Completion (Estimated): July 31, 2027

Study Registration Dates

• First Submitted: October 17, 2026
• First Submitted That Met QC Criteria: November 5, 2026
• First Posted (Actual): November 12, 2026

Study Record Updates

• Last Update Posted (Actual): November 12, 2026
• Last Update Submitted That Met QC Criteria: November 5, 2026
• Last Verified: November 1, 2026

More Information

Terms related to this study

• Keywords: biomarker; exhaled breath; resistance training; treatment response; fat oxidation; breath acetone; tirzepatide
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Overweight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity; Amino Acids, Peptides, and Proteins; Proteins; Glucagon-Like Peptide-1 Receptor; Glucagon-Like Peptide Receptors; Receptors, G-Protein-Coupled; Receptors, Cell Surface; Membrane Proteins; Receptors, Gastrointestinal Hormone; Receptors, Peptide; Tirzepatide
• Other Study ID Numbers: 2026-537-S-CT

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

IPD Plan Description

Individual participant data will not be shared outside the sponsor institution. Aggregated or fully anonymized data may be made available to researchers upon reasonable request to the Principal Investigator.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No