An internet-based virtual coach to promote physical activity adherence in overweight adults: randomized controlled trial

J Med Internet Res. 2012 Jan 26;14(1):e1. doi: 10.2196/jmir.1629.


Background: Addressing the obesity epidemic requires the development of effective, scalable interventions. Pedometers and Web-based programs are beneficial in increasing activity levels but might be enhanced by the addition of nonhuman coaching.

Objectives: We hypothesized that a virtual coach would increase activity levels, via step count, in overweight or obese individuals beyond the effect observed using a pedometer and website alone.

Methods: We recruited 70 participants with a body mass index (BMI) between 25 and 35 kg/m(2) from the Boston metropolitan area. Participants were assigned to one of two study arms and asked to wear a pedometer and access a website to view step counts. Intervention participants also met with a virtual coach, an automated, animated computer agent that ran on their home computers, set goals, and provided personalized feedback. Data were collected and analyzed in 2008. The primary outcome measure was change in activity level (percentage change in step count) over the 12-week study, split into four 3-week time periods. Major secondary outcomes were change in BMI and participants' satisfaction.

Results: The mean age of participants was 42 years; the majority of participants were female (59/70, 84%), white (53/70, 76%), and college educated (68/70, 97%). Of the initial 70 participants, 62 completed the study. Step counts were maintained in intervention participants but declined in controls. The percentage change in step count between those in the intervention and control arms, from the start to the end, did not reach the threshold for significance (2.9% vs -12.8% respectively, P = .07). However, repeated measures analysis showed a significant difference when comparing percentage changes in step counts between control and intervention participants over all time points (analysis of variance, P = .02). There were no significant changes in secondary outcome measures.

Conclusions: The virtual coach was beneficial in maintaining activity level. The long-term benefits and additional applications of this technology warrant further study.

Trial registration: NCT00792207; (Archived by WebCite at

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Body Mass Index
  • Exercise*
  • Humans
  • Internet*
  • Middle Aged
  • Overweight / physiopathology*
  • Patient Compliance*

Associated data