In Mexico, 7 out of 10 adults are overweight or obese. The diseases associated with these conditions (diabetes, cardiovascular disease and some cancers) are those that impact the most on the disability-adjusted life years of Mexicans and on their mortality rates. A reduction in body weight of 5-10% can reduce the incidence of obesity related diseases. The gold standard for treating obesity is an intensive lifestyle change program such as the Diabetes Prevention Program (DPP) whose effectiveness has been evaluated in various formats and populations with positive results, including in Mexico. However, the DPP is not accessible to all sectors of the population. To increase its dissemination, the implementation of online interventions based on the DPP (oi-DPP) has been proposed. A systematic review of oi-DPP showed promising results, however, the evidence is limited and the lack of studies of high methodological quality is highlighted. The main objective of this project is to evaluate the efficacy of an oi-DPP for weight loss in Mexican adults with overweight or obesity at 3 months. The study design is a randomized controlled trial with 2 arms: oi-DPP and wait-list control. A 3 months pilot study (n=30) will be conducted prior to the main study to estimate sample size, considering an alpha error of 0.05 and power of 80%. The primary outcome is the mean change in body weight from baseline to 3 months post-baseline between the 2 groups. Secondarily, differences in biochemical parameters (fasting glucose, total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides and gamma glutamyl transferase) from baseline to 3 months will be evaluated, as well as mean changes from baseline to 3 and 6 months in body mass index, waist circumference, systolic and diastolic blood pressure, depression and quality of life scales and the number of participants achieving a weight loss greater than 5% of initial body weight. Body weight will be also evaluated at 6 months post-baseline. The previous measurements will apply both in the pilot study and the study except for the biochemical parameters that will only be included in the main study. The differences between the 2 groups for each variable will be analyzed using a t test for independent samples, in case of having a parametric sample. Otherwise, the Mann-Whitney U test will be used. Analysis will follow the intent-to-treat principle.

Inclusion Criteria:

• Mexican adults (≥ 18 years and ≤60)
• Residents of the city of Hermosillo, Sonora
• Overweight or obese (BMI ≥ 25 and ≤45)
• Internet access at home
• Basic computer skills
• Facebook active account
• Candidates must make records of their food consumption for 5 days.

Exclusion Criteria:

• Substance abuse
• Consumption of more than 14 alcoholic beverages per week (equivalent to 280 g of alcohol)
• Diagnosis of psychiatric conditions that could prevent adherence to treatment
• Previous diagnosis of medical conditions with significant effect on body weight
• Diagnosis of diabetes
• Systolic blood pressure> 160 mm / Hg
• Pregnant women who are breastfeeding or who plan to become pregnant during the study period
• Consumption of medications with an effect on body weight such as metformin, orlistat or glucocorticoids.
• Participating in another program to reduce weight or performing structured physical exercise other than walking> 180 min / week
• Plan to participate in some treatment for weight loss during the study
• Any other condition in which weight loss or physical activity is contraindicated
• Previous diagnosis of kidney failure, cancer or any other condition that requires special treatment
• Relatives participating in the study
• Have plans to change residence
• Criteria of the researcher - for clinical reasons or adherence to the protocol
• Weight loss>5% of total body weight in the previous 4 months