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.
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
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
Sequential
Exercise snacks programme
BehavioralSix-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.
Conversational agent
BehavioralAutomated 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
DeviceWrist-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.
Standardised physical activity advice
BehavioralA short standardised leaflet on physical activity recommendations and on using the activity tracker, given at baseline. No supervised sessions and no counselling are provided.
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.
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.
Change in peak oxygen uptake (L/min), programme versus active control
Peak oxygen uptake in litres per minute during a maximal walking cardiopulmonary exercise test on a treadmill. Tested only if Primary Outcome 1 is significant.
Change in peak oxygen uptake (L/min), conversational agent versus no further support
Peak oxygen uptake in litres per minute during a maximal walking cardiopulmonary exercise test on a treadmill. Tested only if Primary Outcome 2 is significant.
Fasting plasma glucose
Fasting plasma glucose concentration in millimoles per litre, measured in a venous blood sample taken at the general practice after an overnight fast.
Glycated haemoglobin (HbA1c)
Glycated haemoglobin (HbA1c) concentration in millimoles per mole, measured in a venous blood sample taken at the general practice.
Total cholesterol
Total cholesterol concentration in millimoles per litre, measured in a venous blood sample taken at the general practice after an overnight fast.
Low-density lipoprotein cholesterol
Low-density lipoprotein (LDL) cholesterol concentration in millimoles per litre, measured in a venous blood sample taken at the general practice after an overnight fast.
Click on the lead sponsor to view all of their trials.
Charles University, Czech Republic
Lead sponsor
University of Hradec Kralove
Collaborator
University of Ostrava
Collaborator
This trial is not recruiting at the moment. You can still explore other options:
