The purpose of this research is to study the effect of olive oil rich diet consumption on serum omentin concentration in overweight women. The research is a randomized clinical trial (cross-over). Inclusion Criteria: females age between 20-50-year, BMI between 25-29/9, Exclusion criteria: pregnancy, breast feeding, history of coronary artery disease, diabetes, metabolic diseases, arthritis, lupus, GI diseases, hypertension, any kind of infection, trauma, thyroid diseases, history of using drugs, such as (anti hypertension, anti hyperlipidemia, anti-inflammation, anti diabetic agents, drugs for weight reduction, OCP, corticosteroids). 16 healthy females will participate in the study and will be randomly divided into two groups. Group 1 will receive a diet with energy restriction (-500 kcal), 51% carbohydrate, 15% protein, 34% fat, 16% SFA, 10% PUFA, 8% MUFA. Group 2 will receive a diet with energy restriction (-500 kcal) and rich in extra virgin olive oil with composition: 51% carbohydrate, 15% protein, 34% fat, 8% SFA, 10% PUFA, 16% MUFA. The subjects in each group will follow the diet for six weeks and after two weeks for wash out period the two groups will change place with regard the diet they are receiving. They will follow the new diet for another six weeks. At the beginning and the end of each phase a blood sample (10 cc) will be collected and anthropometric indices will be measured. In addition, a 24-h recall and a physical activity questionnaire will be completed by subjects every other week.