Exercise Snacks Enabled by an mHealth Intervention Delivered in General Practice to Promote a Sustainable Active Lifestyle in Adults With Obesity
SnackFIT
1 other identifier
interventional
306
1 country
3
Brief Summary
Adults with obesity gain as much from regular physical activity as anyone else, but structured exercise programmes are hard to sustain once the programme ends. This trial tests a different approach, built around exercise snacks, that is short bouts of activity of a few minutes at a time, spread through an ordinary day. Physically inactive adults aged 18 to 65 with obesity are invited by their own general practitioner. Everyone who takes part receives a wrist-worn activity tracker and keeps it at the end of the study. Participants are allocated at random in two steps. At the start, two out of every three take part in a six-month programme of supervised group exercise sessions and individual counselling based on motivational interviewing. The remaining third receives the tracker together with brief standardised advice on physical activity. After six months, everyone who took part in the programme is allocated at random a second time, half and half: one half receives an automated conversational agent that supports them by message for the following twelve months, and the other half receives no further support. The trial asks two questions. First, whether the six-month programme increases physical activity compared with the tracker and brief advice alone. Second, whether the automated conversational agent helps participants sustain their activity over the following year. Physical activity is measured with a research-grade accelerometer worn on the wrist for one week at the start, at six months and at eighteen months. Aerobic fitness, cardiometabolic blood markers, physical function and wellbeing are measured at the same three visits.
Trial Health
Trial Health Score
Automated assessment based on enrollment pace, timeline, and geographic reach
participants targeted
Target at P75+ for not_applicable obesity
Started Oct 2026
Typical duration for not_applicable obesity
3 active sites
Health score is calculated from publicly available data and should be used for screening purposes only.
Trial Relationships
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Study Timeline
Key milestones and dates
First Submitted
Initial submission to the registry
September 25, 2026
CompletedStudy Start
First participant enrolled
October 1, 2026
CompletedFirst Posted
Study publicly available on registry
October 9, 2026
CompletedPrimary Completion
Last participant's last visit for primary outcome
March 1, 2029
ExpectedStudy Completion
Last participant's last visit for all outcomes
March 1, 2029
October 9, 2026
October 1, 2026
2.4 years
September 25, 2026
October 7, 2026
Conditions
Keywords
Outcome Measures
Primary Outcomes (2)
Change in device-measured physical activity, programme versus active control
Minutes per day of moderate to vigorous physical activity, measured by a wrist-worn accelerometer worn for seven consecutive days.
Baseline to 6 months
Change in device-measured physical activity, conversational agent versus no further support
Minutes per day of moderate to vigorous physical activity, measured by a wrist-worn accelerometer worn for seven consecutive days.
6 months to 18 months
Secondary Outcomes (2)
Change in peak oxygen uptake (L/min), programme versus active control
Baseline to 6 months
Change in peak oxygen uptake (L/min), conversational agent versus no further support
6 months to 18 months
Other Outcomes (35)
Fasting plasma glucose
Baseline, 6 months, 18 months
Glycated haemoglobin (HbA1c)
Baseline, 6 months, 18 months
Total cholesterol
Baseline, 6 months, 18 months
- +32 more other outcomes
Study Arms (3)
Programme, then conversational agent
EXPERIMENTALMonths 0 to 6: two supervised group sessions, six individual motivational interviewing counselling sessions delivered remotely, and a wrist-worn activity tracker. Months 6 to 18: an automated conversational agent based on a large language model, delivering maintenance support by message.
Programme, then no maintenance support
EXPERIMENTALMonths 0 to 6: identical to Arm 1. Months 6 to 18: no further programme contact; participants keep the tracker.
Active control
ACTIVE COMPARATORA wrist-worn activity tracker and a short standardised leaflet on physical activity recommendations and tracker use, from baseline to 18 months.
Interventions
Six-month lifestyle physical activity programme centred on exercise snacks, that is brief structured bouts of activity distributed across the day. Two supervised group sessions and six individual counselling sessions delivered remotely by video call, based on motivational interviewing and delivered by trained counsellors. The target given to participants is at least 150 intensity minutes per week, based on individual heart-rate thresholds derived from their own cardiopulmonary exercise test.
Automated conversational agent based on a large language model, grounded in motivational interviewing and the Health Action Process Approach, delivered from six to eighteen months through a widely used messaging application and drawing on the participant's own activity data.
Wrist-worn activity tracker showing daily intensity minutes, calibrated to the participant's individual heart-rate thresholds derived from their own cardiopulmonary exercise test. Participants keep the tracker at the end of the study.
A short standardised leaflet on physical activity recommendations and on using the activity tracker, given at baseline. No supervised sessions and no counselling are provided.
Eligibility Criteria
You may qualify if:
- Aged 18 to 65 years
- Body mass index 30.0 to 39.9 kg/m2, that is obesity class I or II
- Registered with a participating general practice
- Physically inactive, defined as meeting neither of the following: at least 150 minutes per week of physical activity, counting moderate-intensity activity once and vigorous-intensity activity twice; or at least two sessions per week of organised exercise
- Willing to wear the study-provided activity tracker for the whole study
- Judged by the general practitioner to be medically fit for a maximal walking treadmill exercise test and for a physical activity programme of moderate to vigorous intensity
You may not qualify if:
- Insufficient command of Czech to take part in counselling and complete questionnaires
- Pregnancy
- Another member of the same household already enrolled in the study
- Significant comorbidity limiting safe participation or adherence, including serious mental illness, advanced cardiac disease, marked mobility limitation and neurological disorders
Contact the study team to confirm eligibility.
Sponsors & Collaborators
- Charles University, Czech Republiclead
- University of Hradec Kralovecollaborator
- University of Ostravacollaborator
Study Sites (3)
University of Ostrava, Faculty of Education
Ostrava, 701 03, Czechia
Institute of General Practice, First Faculty of Medicine, Charles University
Prague, 128 00, Czechia
Faculty of Physical Education and Sport, Charles University
Prague, 162 52, Czechia
MeSH Terms
Conditions
Condition Hierarchy (Ancestors)
Study Officials
- PRINCIPAL INVESTIGATOR
Tomáš Větrovský, MD, PhD
Charles University, Czech Republic
Central Study Contacts
Study Design
- Study Type
- interventional
- Phase
- not applicable
- Allocation
- RANDOMIZED
- Masking
- NONE
- Purpose
- PREVENTION
- Intervention Model
- SEQUENTIAL
- Sponsor Type
- OTHER
- Responsible Party
- PRINCIPAL INVESTIGATOR
- PI Title
- Principal Investigator
Study Record Dates
First Submitted
September 25, 2026
First Posted
October 9, 2026
Study Start
October 1, 2026
Primary Completion (Estimated)
March 1, 2029
Study Completion (Estimated)
March 1, 2029
Last Updated
October 9, 2026
Record last verified: 2026-10
Data Sharing
- IPD Sharing
- Will share
- Shared Documents
- STUDY PROTOCOL, SAP, ICF
- Time Frame
- Beginning 12 months after publication of the primary results, with no end date.
- Access Criteria
- Requests should be directed to the principal investigator. Data will be shared with researchers who provide a methodologically sound proposal, after approval of that proposal and signature of a data sharing agreement.
De-identified individual participant data underlying the results reported in each publication, together with a data dictionary. The exact set of variables will be agreed for each request. Data that could identify a participant will not be shared.