This paper is one in a series developed through a process of expert consensus to provide an overview of questions of current importance in research into engagement with digital behavior change interventions, identifying guidance based on research to date and priority topics for future research. The first part of this paper critically reflects on current approaches to conceptualizing and measuring engagement. Next, issues relevant to promoting effective engagement are discussed, including how best to tailor to individual needs and combine digital and human support. A key conclusion with regard to conceptualizing engagement is that it is important to understand the relationship between engagement with the digital intervention and the desired behavior change. This paper argues that it may be more valuable to establish and promote "effective engagement," rather than simply more engagement, with "effective engagement" defined empirically as sufficient engagement with the intervention to achieve intended outcomes. Appraisal of the value and limitations of methods of assessing different aspects of engagement highlights the need to identify valid and efficient combinations of measures to develop and test multidimensional models of engagement. The final section of the paper reflects on how interventions can be designed to fit the user and their specific needs and context. Despite many unresolved questions posed by novel and rapidly changing technologies, there is widespread consensus that successful intervention design demands a user-centered and iterative approach to development, using mixed methods and in-depth qualitative research to progressively refine the intervention to meet user requirements.

Background Few weight-loss interventions are evaluated for longer than a year, and even fewer employ social and mobile technologies commonly used among young adults. We assessed the efficacy of a two-year, theory-based weight-loss intervention that was remotely and adaptively delivered via integrated user-experiences with 1) Facebook, 2) mobile apps, 3) text messaging, 4) emails, 5) a website, and 6) technology-mediated communication with a health coach. Methods From May 2011 to May 2012, 404 overweight or obese college students (aged 18 to 35 years) from three universities in San Diego, CA were randomized using a computer-based procedure to receive either the intervention (n=202) or general information about health and wellness (control group, n=202). The primary outcome was objectively measured weight in kg at 24 months, and differences between groups were evaluated using linear mixed-effects regression and an intention-to-treat framework. The trial was registered with ClinicalTrials.gov NCT01200459. Findings Participants’ mean (standard deviation (SD)) age was 22·7 (3.8) years. They were 70% female and 31% Hispanic. Mean (SD) body mass index was 29·0 (2.8) kg/m2. At 24 months, weight was assessed in 341 (84%) participants, but all 404 were included in analyses. Weight, adjusted for sex, ethnicity, and college, was significantly less in the intervention group compared to the control group at 6 months (−1·33 kg, 95% confidence interval (CI) = −2·36 to −0·30, p = 0·011) and 12 months (−1·33 kg, 95% CI =−2·30 to −0·35, p = 0·008). However, differences between groups at 18 months (−0·67 kg, 95% CI = −1·69 to 0·35, p = 0·200) and 24 months (−0·79 kg, 95% CI = −2·02 to 0·43, p = 0·204) were not significant. Interpretation Social and mobile technologies may facilitate limited short-term weight loss among young adults, but as utilized in this intervention, these approaches did not produce sustained reductions in weight.

Background Sedentary behavior is recognized as a distinct construct from lack of moderate-vigorous physical activity and is associated with deleterious health outcomes. Previous studies have primarily relied on self-reported data, while data on the relationship between objectively-measured sedentary time and cardiometabolic biomarkers are sparse, especially among U.S. Hispanics/Latinos. Methods and Results We examined associations of objectively-measured sedentary time (via Actical accelerometers for 7 days) and multiple cardiometabolic biomarkers among 12,083 participants, aged 18–74 years, from the Hispanic Community Health Study/Study of Latinos. Hispanics/Latinos of diverse backgrounds (Central American, Cuban, Dominican, Mexican, Puerto Rican, and South American) were recruited from 4 U.S. cities between 2008 and 2011. Sedentary time (<100 counts/minute) was standardized to 16-hour/day of wear time. The mean sedentary time was 11.9 hours/day (74% of accelerometer wear time). After adjustment for moderate-vigorous physical activity and confounding variables, prolonged sedentary time was associated with decreased high-density lipoprotein (HDL)-cholesterol (P=0.04), and increased triglycerides, 2-hour glucose, fasting insulin and HOMA-IR (all P<0.0001). These associations were generally consistent across age, sex, Hispanic/Latino backgrounds, and physical activity levels. Even among individuals meeting physical activity guidelines, sedentary time was detrimentally associated with several cardiometabolic biomarkers (diastolic blood pressure, HDL-cholesterol, fasting and 2-hour glucose, fasting insulin and HOMA-IR; all P<0.05). Conclusions Our large population-based, objectively-derived data showed deleterious associations between sedentary time and cardiometabolic biomarkers, independent of physical activity, in U.S. Hispanics/Latinos. Our findings emphasize the importance of reducing sedentary behavior for the prevention of cardiometabolic diseases, even in those who meet physical activity recommendations.

There are design and administration features of child/adolescent FFQs that should be considered to obtain reliable and valid estimates of dietary intake in this population.