Introduction: Changes in unhealthy lifestyles are key elements in the prevention and treatment of obesity and hypertension. Internet-based programs offer great potential for the implementation of evidence-based interventions focused on promoting healthy habits. We evaluate the efficacy of an Internet-based self-administered program ("Living Better") that addresses people diagnosed as being overweight or having type I obesity and hypertension. Methods: The sample was composed of a total of 106 participants (age Mean = 53; 59 males) from a public hospital in Spain, diagnosed as being overweight or having type I obesity and hypertension and randomized into two groups-the intervention group (IG; Internet-based intervention) and the control group (CG; usual medical treatment). The intervention used cognitive-behavioral strategies and psychoeducation to promote healthy habits. Anthropometric data (i.e., Body Mass Index-BMI-, waist circumference, and hip circumference) and lifestyle/psychological data (i.e., quality of life, physical activity, eating styles, motivation, mood, and self-efficacy) were assessed before and after the intervention, and at 6 and 12-month follow-ups. Results: Significant differences were observed between the IG and the CG in anthropometrical variables after intervention (i.e., BMI and waist circumference), external eating style, and anxiety and stress scores (p < 0.05). Follow-up data showed that changes were maintained in BMI, waist and hip circumference, and external eating in the IG. After receiving the Internet-based treatment, the CG also improved its clinical condition. Discussion: This study demonstrates that the Internet is a viable alternative for the delivery and dissemination of interventions focused on promoting healthy habits, and a totally self-administered intervention can produce long-term positive results. 1. Introduction Lifestyles are one of the most important determinants of health. Sedentary behaviors, consumption of fatty foods, fast food, tobacco, alcoholic beverages, stress, among other factors, are currently the most important causes of mortality and illness [1-3].

Background Internet-based interventions are a promising strategy for promoting healthy lifestyle behaviors. These have a tremendous potential for delivering electronic health interventions in scalable and cost-effective ways. There is strong evidence that the use of these programs can lead to weight loss and can lower patients’ average blood pressure (BP) levels. So far, few studies have investigated the effects of internet-based programs on patients who are obese with hypertension (HTN). Objective The aim of this study is to investigate the short- and long-term efficacy, in terms of body composition and BP parameters, of a self-administered internet-based intervention involving different modules and learning techniques aimed at promoting lifestyle changes (both physical activity and healthy eating) in patients who are obese with HTN. Methods A randomized wait-list controlled trial design was used. We recruited 105 adults with HTN who were overweight or obese and randomly assigned them to either a 3-month internet-based intervention group (n=55) or the wait-list control group (n=50). We assessed BMI (primary outcome), body fat mass (BFM), systolic (S)BP and diastolic (D)BP, blood glucose and insulin levels, physical activity levels, and functional capacity for aerobic exercise at Time 0 (preintervention) and Time 1 (postintervention). All the patients in the wait-list control group subsequently received the intervention, and a secondary within-group analysis, which also included these participants, was conducted at Time 2 (12-month follow-up). Results A 2-way mixed analysis of covariance showed a significant decrease in BMI, BFM, and blood glucose at 3 months in the internet-based intervention group; the effect size for the BMI and BFM parameters was moderate to large, and there was also a borderline significant trend for DBP and insulin. These results were either maintained or improved upon at Time 2 and showed significant changes for BMI (mean difference −0.4, 95% CI −0.1 to −0.6; P=.005), BFM (mean difference −2.4, 95% CI −1.1 to −3.6; P<.001), DBP (mean difference −1.8, 95% CI −0.2 to −3.3; P=.03), and blood glucose (mean difference −2, 95% CI 0 to −4; P=.04). Conclusions Implementation of our self-administered internet-based intervention, which involved different learning techniques aimed to promote lifestyle changes, resulted in positive short- and long-term health benefits in patients who are obese with HTN. Trial Registration ClinicalTrials.gov NCT03396302; https://clinicaltrials.gov/ct2/show/NCT03396302