Over 30% of EU citizens at vulnerable stages and situations in life are at increased risk to transgress from healthy weight to overweight and further to obesity. Though many interventions to tackle obesity have been proposed, they have rarely been effective. The aim of HealthyW8 is to advance the efficacy of current and future efforts and investments in obesity prevention initiatives across Europe. Most interventions suffer from not adapting to personal context (e.g. socioeconomic aspects, host-biological factors, environment, dietary preferences, fitness level etc.), focus only on diet or physical activity alone, do especially overlook emotional aspects, and fail to engage and motivate the user. Thus, initiatives on obesity prevention in policy and practice are often of marginal impact. HealthyW8 will address these shortcomings by iteratively developing, together with stakeholders, a digital-based healthy lifestyle recommender for evidence-based, tailored interventions and tools including a human digital twin to bridge the gap between science, societal actors and stakeholders (e.g. healthcare professionals, food industries, policymakers) and EU citizens. The targeted populations are those undergoing transitions, i.e. schoolchildren (5-10 y, and their parents), young adults (18-25 y) and the elderly (>65 y). In the mid-term, we estimate that with 200,000 HealthyW8 users, we will prevent 10,000 obesity cases/y. In the long run, the impact will be maximized through adopting the project’s proposed methodology, platform and tools by as many EU institutions and entities as possible. HealthyW8 is a highly experienced, synergistic and complementary consortium that will built on a previously developed digital dietary app (LIFANA) and draw on transdisciplinary research in pan-EU multicentre pilots and long-term randomized control trials to achieve its overarching objective of increasing impact of current and future obesity prevention interventions and policies in the EU.