Obesity (Body Mass Index >30 kg/m2), Obesity & Overweight, Overweight (BMI > 25)
Conditions
Keywords
Overweight, Obesity, Breath sensor, Biofeedback, Digital Health, Weight loss, Weight management
Brief summary
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.
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.
Interventions
DEVICEBreath 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.
Sponsors
University of British Columbia
Study design
Observational model
COHORT
Time perspective
RETROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Percent Total Body Weight Loss (TBWL%) at Week 104. | 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). |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Percent Total Body Weight Loss (TBWL%) at Week 52 | 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). |
| Percent Total Body Weight Loss (TBWL%) at Week 24 | 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). |
| Percent Total Body Weight Loss (TBWL%) at Week 12 | 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). |
| Proportion Achieving ≥5% Weight Loss at Week 52 (Observed Case) | 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. |
| Proportion Achieving ≥10% Weight Loss at Week 52 (Observed Case) | 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. |
| Proportion Achieving ≥5% Weight Loss at Week 104 (Observed Case) | 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. |
| Proportion Achieving ≥10% Weight Loss at Week 104 (Observed Case) | 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. |
| Absolute Weight Change (lb) at Week 104 | 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. |
| Absolute Weight Change (lb) at Week 52 | 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. |
| Absolute Weight Change (lb) at Week 24 | 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. |
| Absolute Weight Change (lb) at Week 12 | 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. |
Countries
Canada
Contacts
PRINCIPAL_INVESTIGATORJonathan Little
UBC Okanagan
Outcome results
None listed