Study Population An open invitation is made to children from eight public schools of low socioeconomic status (low SES), representative of all geographical areas of Monterrey, second largest city in México. From those that accept, children will be randomly selected and screened for overweight/obesity using BMI percentiles, and those who qualify for overweight/obesity will be invited to participate in the dietetic intervention program.

Clinical Evaluation Based on the World Health Organization and the American Academy of Pediatrics criteria (BA, Spear, et al., 2007), overweight is considered as BMI \> 85th and \< 95th percentiles and obesity as \> 95th percentile according to age and sex. Anthropometric measurements will be performed in all participants at each school. Standing height will be determined to the nearest 0.5 cm (portable Seca® stadiometer, North America) and weight to the nearest 0.1 kg while children wear light clothing, no socks or shoes (TANITA TBF 300® scale, Arlington, Illinois). Waist circumference will be measured to the nearest 0.1 cm at the level of the umbilicus with a flexible fiberglass tape while the subjects are standing, after gently exhaling, and with no clothing on the area. BMI will be calculated by weight (kg) divided by the square of height (m). Measurements will be performed by the same three trained registered dietitians (RD) in all children to control the inter-observer variability.

Dietetic Intervention The principal strategies for the change in energy and food groups consumption, are dietary modifications for the children and parental support, as recommended by national associations (SR, Daniels et al, 2009; TA, Nicklas, et al, 2008; BA, Spear, et al., 2007, A Report of the Panel on Macronutrients et al, 2005). Dietetic intervention will be given individually by a RD for every child at each school, every three weeks, for a total of 13 visits during the school-year. Children will leave the classroom to attend the 30-minute nutrition counseling. Each child will be seen by the same RD throughout the school-year to favor compliance to the plan and to avoid inter-examiner bias. Each session will consist of: 1.) Anthropometric assessment; 2.) Dietetic assessment by means of 24-hour diet recalls, a standardized food frequency questionnaire that included Mexican foods, and food replicas to aid in estimation of portion sizes; 3.) Individualized energy restriction and balanced macronutrient dietary planning; 4.) Provision of structured, tailored-made daily menus and meals for the next three weeks for each child; and 5.) Information given to parents/care givers about healthy food, eating practices and portion sizes. Attendance of the parent/care giver is mandatory to help answer the 24-hour recalls and to assure commitment to follow the dietary recommendations at home. After each visit, the RD will record the information into the software (NutriKcal®VO software, Consinfo S.C., D.F., Mexico.), which determines energy intake and diet composition.

Diet composition (macronutrients) is based on the most recent dietary recommended intake for children (A Report of the Panel on Macronutrients et al, 2005) : 25%-35% of total calories from fat; 45%-65% from carbohydrates and 10%-30% from protein. Additional recommendations for children or adolescents include a variety of foods low in saturated fat (\<10% kcal), no trans fat and cholesterol \<300 mg/day. The RDs will promote age appropriate serving sizes, including approximately \>5 servings of fruit and vegetables, \>3 servings of low fat milk or dairy products, \>6 servings of whole-grain products per day; increase of dietary fiber and reduction of salt intake (US Department of Agriculture and US Department of Health and Human Services, 2010). As well, children will be advised to avoid overconsumption of energy dense, nutrient-poor foods and beverages (TA, Nicklas et al, 2008).

Reduction in calorie intake is approached following the recommendations of the American Heart Association in which children \> 4 years old with a BMI \> 85th percentile to achieve BMI percentile reductions to \<85th percentile with weight maintenance during linear growth (SR, Daniels, et al, 2009). As advised (BA, Spear, et al, 2007), progressive restriction of 150-900 calories from actual intake throughout the school year is recommended so that obese children with BMI \>95th percentile lose gradually 0.5 kilogram/month and those with BMI \>99th percentile lose a maximum of 0.9 kilogram/week.

Statistical Methods MINITAB version 16 (Minitab Inc., State College, Pennsylvania, USA) will be used to analyze the differences between anthropometric parameters and nutrient intake values at baseline and end of intervention; Microsoft Excel 2007 (Microsoft Corp., Redmond, Washington, USA) will be used to incorporate the input of data. The results will be expressed as mean ± standard deviation (s.d.) and their corresponding 95% confidence intervals (CI). Comparisons between groups for dependent variables will be made using paired Student's t-test for means. The mean comparisons between gender groups will be determined using t-test for independent samples. All tests will be interpreted based on two-tailed hypothesis. The significance level will be set at 0.05 in all cases.