The EAT-Lancet Commission proposed the planetary health diet as a strategy to achieve health and sustainability goals. Currently, its effect in the treatment of obesity has not been evaluated. The main aim is to evaluate the efficacy of the planetary health diet included in an intensive lifestyle change program compared to a waiting list group, on weight and body fat at 4 months, in Mexican adults with overweight or obesity, in an online modality. This study is a 4-month randomized controlled trial, in an online modality in individuals with overweight or obesity randomly assigned 1:1:1 to one of three groups: 1) planetary health diet, 2) waiting list and 3) low fat-diet. The primary outcome is the difference in change in weight (kg) and body fat (kg) at 4 months between the planetary health diet group and the waiting list group. Comparison with the low-fat diet group will be an exploratory analysis. Secondary variables include changes in waist circumference, BMI, blood pressure, and health-related quality of life. Between group comparisons will be analyzed by intention-to-treat. The protocol was approved by a Research Bioethics Committee.

The present study is a randomized controlled trial of parallel groups and superiority. The sample will consist of 60 participants (20 participants for each arm of the study), calculated from previous studies of our research group. The intervention groups will be 1) planetary health diet, 2) waiting list group, and 3) low-fat diet.

Participants will be measured at the start of the study and at 4 months. The participants of the two diets will follow the Diabetes Prevention Program (DPP) adapted to the Mexican population and its online application. It has also been adapted for the planetary health diet group.

Participants will receive 13 online group educational sessions over 4 months (1 per week) and at least one individual session per week. They will receive a meal plan according to the dietary group to which they belong, with a calorie range from 1200 to 1800 kcal.

Participants in the waiting list group will receive digital information on healthy eating. Upon completion of the study, they will be invited to participate in the "Lifestyle Balance Program" offered at the Nutritional Health Promotion Center, which is an adaptation of the DPP. During the 4 months, there won't be any contact with this group.

The analysis of the primary and secondary outcomes will be carried out in a conservative way by intention to treat and also by completers analysis.

Inclusion Criteria:

• Mexican adults (≥18 and ≤60 years).
• Residents of the city of Hermosillo, Sonora.
• BMI ≥ 25 kg/m2 and ≤ 40 kg/m2.
• Availability of time to participate in the study
• Have an electronic device with internet access
• Completion of a dietary record for at least 2 days prior to the intervention.
• Active Facebook account, telephone number, WhatsApp and/or e-mail address
• Basic computer skills

Exclusion Criteria:

• Illiteracy
• Present health conditions due to previous diagnosis with effect on body weight, or that prevent adherence to the intervention (Diabetes, hypertension with values ≥ 150/95 mm Hg, liver failure)
• Pregnancy or lactation.
• History of weight loss in the last 4 months of > 5% of total body weight.
• Being 10% below usual weight.
• Surgeries aimed at weight and/or body fat reduction.
• Use of medications or substances with effect on body weight, e.g. metformin, orlistat, corticosteroids, etc.
• Use of addictive substances
• Plan to change residence during the 4 months of the study.
• Other family member who has agreed to participate in the study.
• History of COVID-19 that required hospitalization or needed for supplemental oxygen or developed sequelae that precludes intervention.

The database and results of the study are available from the corresponding author on reasonable request.

Undefined

Direct communication with the corresponding authors.