The clinical study aimed to study the effect of an intervention with foods containing folate and hazelnut oil to assess whether this diet could modulate the methylation levels of two obesity-related genes, LEP and POMC, in addition to impacting body weight and values of lipid profile of overweight women. The hypothesis of the clinical study is that the intervention diet could reduce the methylation levels of the genes mentioned and this would impact on the reduction of body weight and improvement of the lipid profile of the women studied.

The intervention study was carried out with a sample selected by randomization, and n = 40 adult women classified as overweight were considered for the study. After assessing the eligibility criteria, women were instructed to have stable weight, eating habits and levels of physical activity constant to those found during the baseline, as well as receiving an individual diet plan one week before starting the dietary intervention. Before the start of the intervention, the 40 women were allocated to four groups of 10 each, and three groups started the individual diet plan for weight maintenance with a focus on vegetables and legumes with antioxidant and folate-rich action, and were also invited to consume foods fortified with folic acid and foods naturally rich in folate to achieve a usual folate intake close to the RAS (≥400 µg), this amount was for intervention group 1 and 2, group 3 received a lower amount (approximately half of the consumption of groups 1 and 2) and group 4 was the control group.

Still referring to the intervention, the participants of the three groups received advice from a nutritionist, responsible for this research and all the printed material free of charge, including pre-packaged foods, and also delivered hazelnut oil capsules, used as a source of monounsaturated fat. Counseling sessions with the nutritionist were offered daily at the homes during the entire period of the intervention, except for group 4, where the monitoring was weekly, to maintain eating habits.

After the end of the 8 weeks of the intervention, the third stage of the study began, which consisted of anthropometric assessment, analysis of the dietary intake of the 24-hour food record and blood collection for biochemical tests and DNA methylation.

Inclusion Criteria:

• Adult women, aged between 20 and 59 years;
• Women with classification of overweight and obesity;
• Women who signed the informed consent form.

Exclusion Criteria:

• Women who changed their lifestyle 3 months before the study started;
• Alcoholic women or smokers;
• Taking medications known to interfere with folic acid metabolism (in the past 3 months), such as antacids and anticonvulsants;
• Individuals who use supplements in general, such as fish oil or other fatty acids;
• Pregnant or planning to become pregnant during the study period.

Sociodemographic data, food consumption, anthropometric assessment, biochemical tests and DNA methylation of the participants. And all the statistical data that support the study.

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