Real-World Two-Year Weight Loss Outcomes With Breath Biofeedback

February 17, 2026 updated by: Jonathan Little, University of British Columbia

Real-World Durability of Weight Loss With a Breath Biofeedback mHealth Program: Two-Year Outcomes in Adults With Overweight or Obesity

The goal of this retrospective observational study is to evaluate the real-world durability of weight loss among adults with overweight or obesity who used the Key to Health breath-biofeedback mHealth program. The main questions it aims to answer are:

  1. What is the mean percent total body weight loss (TBWL%) at 104 weeks after program start?
  2. What are the TBWL% estimates at 12, 24, and 52 weeks, and what proportion of users achieve clinically meaningful weight loss (≥5% and ≥10%) at 52 and 104 weeks (observed case)?

Users initiated the program between Nov 2018 and Apr 2023; follow-up data (weights/engagement) were collected through Apr 2025 to allow up to 104 weeks of observation.

There is no randomized comparison group. Participants will not be asked to do anything beyond normal app use; the study will analyze existing, de-identified weight and engagement data collected during routine program use.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

This is a retrospective, observational real-world evidence study using de-identified backend data from commercially active users of the Key to Health digital weight loss program between November 2018 and April 2025. Eligible users are adults (≥18 years) with a valid onboarding baseline weight and at least one post-baseline weight entry; users must meet the pre-specified baseline BMI threshold for overweight/obesity. Baseline weight is defined as the self-reported onboarding weight. Follow-up weights are defined as user-entered or connected-scale weights recorded after onboarding.

Weight outcomes are assigned to prespecified follow-up windows at Weeks 12, 24, 52, and 104 using a deterministic rule: the weight entry closest to each target day within its window (earlier chosen if equidistant). The primary endpoint is TBWL% at Week 104, defined as (post-baseline weight - baseline weight) / baseline weight × 100. Secondary outcomes include TBWL% at Weeks 12, 24, and 52; absolute weight change; and observed-case responder summaries at Weeks 52 and 104.

The primary analysis will estimate longitudinal TBWL% across visits using a Mixed Model for Repeated Measures (MMRM) with visit as a categorical factor and adjustment for baseline covariates (e.g., baseline weight, age, sex, cohort year). Missing data will be handled under a Missing At Random (MAR) framework inherent to the MMRM approach (no single-value imputation in the primary analysis). Pre-specified sensitivity analyses may be conducted as feasible (e.g., conservative assumptions for missing Week-104 outcomes and weighted approaches for differential observation), with any deviations from the prespecified plan documented.

Study Type

Observational

Enrollment (Actual)

11524

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Canada
    • British Columbia
      • Kelowna, British Columbia, Canada, V1V 1V7
        • UBC Okanagan

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Commercial users of the Key to Health digital weight loss program (mobile app) who enrolled and used the program during the data collection window. Users are members of the general community who accessed the program through routine commercial availability (direct-to-consumer), and who recorded weight measurements during typical use of the app and/or a connected scale. De-identified backend program data were used for this retrospective analysis.

Description

Inclusion Criteria:

  • Adults aged ≥18 years at program start/onboarding
  • Program start date between November 2018 and April 2023
  • Valid baseline (onboarding) self-reported weight recorded
  • Baseline BMI >25 kg/m²
  • At least one valid post-baseline weight entry recorded after onboarding (manual and/or connected scale)

Exclusion Criteria:

  • Missing or invalid baseline weight
  • Biologically implausible baseline weight (per prespecified data-quality checks)
  • No post-baseline weight data recorded after the baseline date/onboarding timestamp

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Key to Health Program Users (Commercial Cohort)
Adults with overweight or obesity who enrolled in and used the Key to Health breath-biofeedback mHealth weight-loss program during the data collection window and had a valid onboarding baseline weight plus at least one post-baseline weight entry recorded via the app and/or a connected scale.
Device: Breath acetone biofeedback device with mHealth program
A breath acetone biofeedback device used alongside the Key to Health mobile app as part of a comprehensive weight-loss program. Users obtain breath acetone readings via the device and record body weight via manual entry and/or connected scale. The app provides program resources to support behavior change, including a food database/food logging tools, nutrition and exercise education (lessons, articles, and other content), alerts/notifications, and engagement features (e.g., streaks and progress tracking). This study retrospectively analyzes de-identified data generated during routine program use; no study-specific procedures are administered.
Other Names:
  • Key to Health Breath Sensor
  • Key to Health Program
  • Keyto Breath Acetone Device
  • Keyto Breath Acetone Sensor

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Percent Total Body Weight Loss (TBWL%) at Week 104.
Time Frame: Week 104 (target Day 728; visit window Days 668-788 after program start).
TBWL% at Week 104 is defined as: (post-baseline weight - baseline weight) / baseline weight × 100, where baseline weight is the self-reported onboarding weight. The Week-104 weight is the post-baseline weight entry closest to Day 728 within the prespecified visit window (Days 668-788; earlier selected if equidistant).
Week 104 (target Day 728; visit window Days 668-788 after program start).

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Percent Total Body Weight Loss (TBWL%) at Week 52
Time Frame: Week 52 (target Day 364; visit window Days 334-394)
TBWL% defined as (post-baseline weight - baseline weight) / baseline weight × 100, where baseline weight is the self-reported onboarding weight. The Week-52 weight is the post-baseline weight entry closest to Day 364 within the visit window (Days 334-394; earlier selected if equidistant).
Week 52 (target Day 364; visit window Days 334-394)
Percent Total Body Weight Loss (TBWL%) at Week 24
Time Frame: Week 24 (target Day 168; visit window Days 138-198)
TBWL% defined as (post-baseline weight - baseline weight) / baseline weight × 100. The Week-24 weight is the post-baseline weight entry closest to Day 168 within the visit window (Days 138-198; earlier selected if equidistant).
Week 24 (target Day 168; visit window Days 138-198)
Percent Total Body Weight Loss (TBWL%) at Week 12
Time Frame: Week 12 (target Day 84; visit window Days 69-99)
TBWL% defined as (post-baseline weight - baseline weight) / baseline weight × 100. The Week-12 weight is the post-baseline weight entry closest to Day 84 within the visit window (Days 69-99; earlier selected if equidistant).
Week 12 (target Day 84; visit window Days 69-99)
Proportion Achieving ≥5% Weight Loss at Week 52 (Observed Case)
Time Frame: Week 52 (target Day 364; visit window Days 334-394)
Proportion of users with TBWL% ≤ -5% at Week 52 among users with an observed in-window Week-52 weight (Days 334-394). TBWL% defined as (post-baseline weight - baseline weight) / baseline weight × 100.
Week 52 (target Day 364; visit window Days 334-394)
Proportion Achieving ≥10% Weight Loss at Week 52 (Observed Case)
Time Frame: Week 52 (target Day 364; visit window Days 334-394)
Proportion of users with TBWL% ≤ -10% at Week 52 among users with an observed in-window Week-52 weight (Days 334-394). TBWL% defined as (post-baseline weight - baseline weight) / baseline weight × 100.
Week 52 (target Day 364; visit window Days 334-394)
Proportion Achieving ≥5% Weight Loss at Week 104 (Observed Case)
Time Frame: Week 104 (target Day 728; visit window Days 668-788)
Proportion of users with TBWL% ≤ -5% at Week 104 among users with an observed in-window Week-104 weight (Days 668-788). TBWL% defined as (post-baseline weight - baseline weight) / baseline weight × 100.
Week 104 (target Day 728; visit window Days 668-788)
Proportion Achieving ≥10% Weight Loss at Week 104 (Observed Case)
Time Frame: Week 104 (target Day 728; visit window Days 668-788)
Proportion of users with TBWL% ≤ -10% at Week 104 among users with an observed in-window Week-104 weight (Days 668-788). TBWL% defined as (post-baseline weight - baseline weight) / baseline weight × 100.
Week 104 (target Day 728; visit window Days 668-788)
Absolute Weight Change (lb) at Week 104
Time Frame: Week 104 (target Day 728; visit window Days 668-788)
Absolute weight change in pounds at Week 104, defined as post-baseline weight at Week 104 minus baseline self-reported onboarding weight. Week-104 weight selected as the entry closest to Day 728 within Days 668-788.
Week 104 (target Day 728; visit window Days 668-788)
Absolute Weight Change (lb) at Week 52
Time Frame: Week 52 (target Day 364; visit window Days 334-394)
Absolute weight change in pounds at Week 52, defined as post-baseline weight at Week 52 minus baseline self-reported onboarding weight. Week-52 weight selected as the entry closest to Day 364 within Days 334-394.
Week 52 (target Day 364; visit window Days 334-394)
Absolute Weight Change (lb) at Week 24
Time Frame: Week 24 (target Day 168; visit window Days 138-198)
Absolute weight change in pounds at Week 24, defined as post-baseline weight at Week 24 minus baseline self-reported onboarding weight. Week-24 weight selected as the entry closest to Day 168 within Days 138-198.
Week 24 (target Day 168; visit window Days 138-198)
Absolute Weight Change (lb) at Week 12
Time Frame: Week 12 (target Day 84; visit window Days 69-99)
Absolute weight change in pounds at Week 12, defined as post-baseline weight at Week 12 minus baseline self-reported onboarding weight. Week-12 weight selected as the entry closest to Day 84 within Days 69-99.
Week 12 (target Day 84; visit window Days 69-99)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of British Columbia

Investigators

  • Principal Investigator: Jonathan Little, UBC Okanagan

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

November 18, 2018

Primary Completion (Actual)

April 25, 2025

Study Completion (Actual)

April 25, 2025

Study Registration Dates

First Submitted

February 17, 2026

First Submitted That Met QC Criteria

February 17, 2026

First Posted (Actual)

February 24, 2026

Study Record Updates

Last Update Posted (Actual)

February 24, 2026

Last Update Submitted That Met QC Criteria

February 17, 2026

Last Verified

February 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 20260202

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Individual participant data will not be shared because the dataset is derived from a commercial digital health program and contains sensitive user-level information. Only de-identified and aggregated results will be reported, and any data sharing would be subject to applicable privacy, consent, and contractual restrictions.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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