Exercise Snacks Enabled by an mHealth Intervention Delivered in General Practice to Promote a Sustainable Active Lifestyle in Adults With Obesity

Condition(s) studied

Investigational drug(s) / intervention(s)

Exercise snacks programme: 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.

Conversational agent: 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: 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.

Standardised physical activity advice: 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.

Study 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.

Eligibility

Primary outcome measure(s)

• Change in device-measured physical activity, programme versus active control — Baseline to 6 months
  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 — 6 months to 18 months
  Minutes per day of moderate to vigorous physical activity, measured by a wrist-worn accelerometer worn for seven consecutive days.

Trial sites (3)

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