Journal of Medical Internet Research - International Scientific Journal for Medical Research, Information and Communication on the Internet #Preprint #PeerReviewMe: Warning: This is a unreviewed preprint. Readers are warned that the document has not been peer-reviewed by expert/patient reviewers or an academic editor, may contain misleading claims, and is likely to undergo changes before final publication, if accepted, or may have been rejected/withdrawn. Readers with interest and expertise are encouraged to sign up as peer-reviewer, if the paper is within an open peer-review period. Please cite this preprint only for review purposes or for grant applications and CVs (if you are the author). Background: Maintaining weight after weight loss is a major health challenge, and eHealth solutions may be one way to meet this challenge. Application of behavior change techniques (BCTs) and persuasive system design (PSD) principles in eHealth development may contribute to design of technologies that positively influence behavior and motivation to support the sustainable health behavior change needed. Objective: To identify BCTs and PSD principles stimulating motivation and adherence in eHealth interventions supporting weight maintenance following weight loss. Methods: A systematic literature search was performed in the databases: PsycInfo, Ovid Medline, Embase, Scopus, Web of Science, and Amed, from January 1, 2007 to June 30, 2018. Arksey and O’Malley scoping review methodology was applied, using Michie´s Behavior Change Taxonomy and the Persuasive System Design-model to identify techniques and principles used. Publications on eHealth interventions were included if focused on weight loss or weight loss maintenance, in combination with motivation or adherence and behavior change. The main focus of this review was on weight loss maintenance. However, eHealth interventions targeting weight loss were also examined, particularly for weight loss maintenance related factors. Results: The search identified 317 publications, of which 45 met the inclusion criteria. Eleven focused on weight loss maintenance and 34 on weight loss. Smartphone (n=28) was the most frequently used technology. Frequently used wearables or sensors were activity trackers or step-counters (n=14), as well as other monitoring technologies such as wireless or digital scales (n=8). Several interventions had a human support component in a blended care format (n=27). Feedback and monitoring and goals and planning were core BCT clusters applied in the majority of included publications. Social support and associations through prompts and cues to support and maintain new habits were more frequently used in weight loss maintenance than weight loss interventions. In both types of interventions, frequently applied PSD principles were self-monitoring, goal-setting and feedback. Tailoring, reminders, personalization and rewards were additional principles frequently applied in weight loss maintenance interventions. Results did not reveal an “ideal” combination of BCTs or PSD principles to stimulate motivation, adherence and weight loss maintenance. The most frequently mentioned individual BCTs and PSD principles applied to stimulate motivation were however personalization, praise and feedback, while associations were frequently mentioned to stimulate adherence. eHealth interventions that found significant effects for weight loss maintenance all applied self-monitoring, feedback, goal-setting, and shaping knowledge, combined with a human social support component. Conclusions: To our knowledge, this is the first review examining key BCTs and PSD principles applied in weight loss maintenance interventions compared with those of weight loss interventions. The most successful eHealth weight loss maintenance interventions entailed a combination of BCTs and PSD principles, including tailoring, self-monitoring, feedback, goals and planning, and shaping knowledge to support creation and establishment of healthy habits and behaviors. The current review identified several techniques and principles applied to stimulate motivation and adherence. Future research should however aim to examine which eHealth design combinations can be the most effective in support of long-term behavior change and weight loss maintenance.