Effectiveness of a Precision Diet Based on Gene Expression Versus a Personalized Mediterranean-Style Diet in Weight Loss

The present randomized controlled trial aims to evaluate the relationship between gene expression profiling and the response to a precision diet compared to a personalized Mediterranean-style diet (control diet) in metabolically healthy individuals with overweight and obesity.

Compared to the control diet, the precision diet is expected to increase adherence to dietary recommendations (resulting in weight loss and maintenance). In addition, the investigators postulate that the precision diet will lead to greater lifestyle changes, improving long-term well-being and health in people with overweight and obesity.

The study aims to evaluate the effectiveness of a precision diet based on gene expression versus a personalized Mediterranean-style diet. For this purpose, a 12-week parallel randomized controlled trial will be conducted. Once eligible participants are recruited, each volunteer will attend two clinical visits (at baseline-week 0 \[T0\], and week 12 \[T1\]), a study initiation visit (at week 1), and three online follow-up visits (at weeks 3, 6 and 9).

First, the participants will come to the baseline visit \[T0\] in which, the investigators will collect data related to health status, body composition, lifestyle, and well-being. In addition, a registered nurse will collect a blood sample for gene expression profiling, along with other biochemical parameters, such as glycemic and lipid markers.

In the following days, the biochemical results from the baseline visit will be evaluated to confirm that the volunteers are metabolically healthy. For this reason, it will not be until seven days after the baseline visit that the eligibility of the participants will be confirmed. After this confirmation, participants will be scheduled for the study initiation visit.

At this visit, the volunteers will be randomly assigned to one of the two study arms, intervention (precision diet) or control diet. Those assigned to the intervention arm will follow the precision diet (a hypocaloric Mediterranean-style diet based on gene expression), while those assigned to the control arm will follow the control diet (a personalized hypocaloric Mediterranean-style diet without considering gene expression).

Then, 12 weeks after the start of the intervention, the end of the intervention \[T1\] will be scheduled, in which the investigators will evaluate the same variables as in the baseline visit \[T0\]. In addition, during the 12 weeks of the study, both groups will attend three online follow-up visits (every 3 weeks) to ensure adherence to the intervention, as well as continuous care and to adapt dietary recommendations when needed.

Eligibility Criteria:
Inclusion Criteria:

* BMI 26-35 Kg/m\^2.
* Metabolically healthy.

Exclusion Criteria:

* Any comorbidity associated with obesity (such as type 2 diabetes mellitus, hypertension, dyslipidemia).
* Medications (Antidepressants; Antipsychotics; Anxiolytic; Statins; Antihypertensives; Insulin or anti-diabetics).
* Intragastric balloon or Bariatric surgery.
* History of weight loss treatment within the previous 3 months.
* Women with menopause, pregnancy, or breastfeeding.
* Smokers.
* Food allergies or intolerances.
* Eating disorders.
* Shift work.