Development of a Nutrigenetic Test for Personalized Prescription of Body Weight Loss Diets (Obekit)

This study evaluates the relationship between several genetic variants and the response to a hypocaloric diet, in order to design a genetic test which permits prescribe the more personalized diet for each individual according to her genotype. Half of the participants will assigned to a moderate high protein diet, while the other half will assigned to a high carbohydrate diet.

Obesity has reached epidemic proportions becoming a major global public health challenge since it is associated with an increased risk of type 2 diabetes, cardiovascular disease, stroke, arthritis and some forms of cancer. Therefore, a large number of strategies have been investigated in order to induce a negative energy balance and consequently body weight loss mainly inducing a low calorie diet and sometimes accompanied by an increase in physical activity. However, individual responses to body weight loss interventions vary widely and several studies have aimed to identify psychological, behavioral and personal predictors of this variability.

In this context, the hypothesis of the present study is that part of the interindividual variability in relation to the success of certain weight loss treatments is based on gene-diet interactions. Depending on the composition of the diet and the genotype of each individual, it is more or less easy to reduce and maintenance body weight.

After the recruitment and selection of the study participants, the study will consists of a 4-month hypocaloric diet ("body weight loss period") followed by a second 6-month period ("body weight maintenance period") in which the subjects of the study will continue with the diet, but without any energy restriction. The participants will assigned to one of the two hypocaloric diets (-30% of the studied requirements for each individual) with different macronutrient composition:

* Moderately high protein diet: 40% of the energy derived from carbohydrates, 30% of the energy derived from protein and 30% of the energy derived from fat.
* Low fat diet: 60% of the energy derived from carbohydrates, 30% of the energy derived from protein and 30% of the energy derived from fat.

A group of normal weight individuals (n 12) will be recruited in order to compare the different parameters obtained in the obese subjects with those of normal population. They will be not subjected to any intervention.

Eligibility Criteria:
Inclusion Criteria:

* Body Mass Index (BMI) between 25 and 40 kg/m2
* Physical examination and vital signs normal, or is considered abnormal, but clinically insignificant by researcher.
* In the case of individuals with chronic stable dose drug treatment and during the last 3 previous months at baseline, the investigator will assess their possible inclusion.

Exclusion Criteria:

* BMI less than 25 or higher than 40 kg/m2
* Pregnant women
* Breastfeeding period. If artificial feeding until 6 months after birth.
* Type 1 diabetes
* Severe kidney diseases
* Severe digestive system diseases
* Electrolyte disorders (disorders of sodium, potassium, calcium, chlorine, phosphorus, magnesium)
* Acute cardiovascular diseases
* Cancer
* Anemia
* Eating disorders
* Recent prescription drug treatment (without stable doses scheduled)
* Drug therapy that can influence weight loss as corticosteroids.
* Some type of cognitive impairment and / psychic
* Subjects in which poor collaboration or, in the investigator's opinion, have difficulty following the procedures of the study is foreseen
* Lack of commitment (at the discretion of the investigator) with the intervention, suspected non-compliance, or real difficulties to follow the development of the study.