Communication of Health Messages
: A Personalised Chatbot for Weight Loss Maintenance

  • William Holmes

Student thesis: Doctoral Thesis


Weight loss and maintenance are improved by effective communication. Technology-based interventions may improve short term behaviour change however many have used older technology such as text-messaging. The long-term benefits of technology are unknown, as is the effectiveness of chatbots (conversation-driven user interfaces) for delivering weight loss maintenance interventions. WeightMentor is a personalised motivational chatbot for weight loss maintenance.
The aim of this PhD was to design, develop, and test the usability of WeightMentor, a personalised motivational chatbot to assist individuals with weight loss maintenance.
This PhD was a mixed methods technology design and development project, comprising five individual studies: a review of literature relating to technology for weight loss maintenance, a needs analysis of the WeightMentor target users, designing and developing the WeightMentor chatbot, testing the usability of the WeightMentor chatbot, and validating the Chatbot Usability Questionnaire (CUQ), designed for measuring chatbot usability.
Key Results
The needs analysis identified five key themes: “Weight loss maintenance is a challenge”, “Social contact can be a double-edged sword”, “Apps are popular”, “Personalised messages are more useful” and “Chatbots have potential for weight loss maintenance”. Participants considered the WeightMentor prototype to be engaging and simple. WeightMentor was designed using contemporary technologies to implement features that would be most useful for target users. WeightMentor scored well above conventional usability benchmarks. The minimum number of users required to identify most usability issues was 39, more than conventional wisdom suggests (n=5-8). During validation the CUQ demonstrated construct validity and test-retest reliability.
Weight loss maintenance is a challenge that may be supported using technology, and the newly developed chatbot, WeightMentor has the potential for weight loss maintenance as it is usability acceptable and is a solution that should be explored further.
Date of AwardMay 2020
Original languageEnglish
SupervisorVivien Coates (Supervisor), Huiru (Jane) Zheng (Supervisor), Anne Moorhead (Supervisor) & Raymond Bond (Supervisor)


  • E-Health
  • Telehealth
  • Behaviour Change
  • Conversational Agents
  • Conversational AI
  • Artificial Intelligence

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