Background Research increasingly supports the conclusion that well-designed programs delivered over the Internet can produce significant weight loss compared to randomized controlled conditions. Much less is known about four important issues addressed in this study: (1) which recruitment methods produce higher eHealth participation rates, (2) which patient characteristics are related to enrollment, (3) which characteristics are related to level of user engagement in the program, and (4) which characteristics are related to continued participation in project assessments.Methods We recruited overweight members of three health maintenance organizations (HMOs) to participate in an entirely Internet-mediated weight loss program developed by HealthMedia, Inc. Two different recruitment methods were used: personal letters from prevention directors in each HMO, and general notices in member newsletters. The personal letters were sent to members diagnosed with diabetes or heart disease and, in one HMO, to a general membership sample in a particular geographic location. Data were collected in the context of a 2×2 randomized controlled trial, with participants assigned to receive or not receive a goal setting intervention and a nutrition education intervention in addition to the basic program.Results A total of 2311 members enrolled. Bivariate analyses on aggregate data revealed that personalized mailings produced higher enrollment rates than member newsletters and that members with diabetes or heart disease were more likely to enroll than those without these diagnoses. In addition, males, those over age 60, smokers, and those estimated to have higher medical expenses were less likely to enroll (all P < .001). Males and those in the combined intervention were less likely to engage initially, or to continue to be engaged with their Web program, than other participants. In terms of retention, multiple logistic regressions revealed that enrollees under age 60 (P < .001) and those with higher baseline self-efficacy were less likely to participate in the 12-month follow-up (P = .03), but with these exceptions, those participating were very similar to those not participating in the follow-up.Conclusions A single personalized mailing increases enrollment in Internet-based weight loss. eHealth programs offer great potential for recruiting large numbers of participants, but they may not reach those at highest risk. Patient characteristics related to each of these important factors may be different, and more comprehensive analyses of determinants of enrollment, engagement, and retention in eHealth programs are needed.

THE FUNDAMENTAL requirement for ethical treatment of research participants is that they give informed consent for their participation. Although there have been a few empirical studies of the consequences of informed consent (e.g., Singer, 1978), researchers need to know much more about the impact of this requirement on research results. This paper reports our findings regarding the consequences of obtaining written parental permission for research participation by minor students.Abstract The parents of an eligible sample of 1618 students in grades four through twelve were contacted to obtain written permission for their children to complete questionnaires related to alcohol and drugs. The distributions of students across the parental response categories (consent-denied, no-reply, or consent-granted) were compared on the student variables of sex, grade level, ethnic group, and reading and vocabulary test scores. The explicit consent procedure produced a sample that was approximately half the size of the eligible population and overrepresented white students while underrepresenting blacks and Asian Americans. There was no evidence of sample bias with respect to student gender, and the evidence regarding bias on academically related measures was mixed.

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