Intervention Study With Omega-3 Fatty Acids for Weight Loss and Insulin Resistance in Adolescents

Background: In 2006, the prevalence of overweight and obesity combined in scholar and adolescents in Mexico was 26% and 31% respectively, which represents more than double of that reported in year 2000. Together with such increments in the obesity rates, it was observed similar increases in the incidence of other metabolic conditions such as insulin resistance (IR). In a very simplistic manner, it seems that the link between obesity and IR is a chronic inflammatory status because the adipose tissue-derived inflammatory molecules interfere with the uptake of fatty acids and glucose in peripheral tissues. On the other hand, it is accepted that the long-chain polyunsaturated fatty acids (LCPUFA) omega-3 exhibit anti-inflammatory properties. In addition, it has been also demonstrated the beneficial effect exerted by such fatty acids on insulin sensitivity, and in stabilizing the weight lost achieved with hypocaloric diets. At present, the prevalence of overweight and obesity combined are in the range of 41-43% in the adolescent population that attend the four areas of influence of the Mexican Institute of Social Security (IMSS) in Mexico City. Interventions addressed to improve the nutritional status of these groups of age are expected to impact the risk for IR and its associated co-morbidities. Objective: To evaluate the impact of supplementation with LCPUFA omega-3, together with a dietary strategy, on obesity and insulin resistance in a sample of obese adolescents attended in the IMSS. Methods: In a randomized clinical design, 300 obese individuals, 12-18 years old, will be selected. At selection, individuals will be randomly assigned to receive daily a capsule with 1.1 g LCPUFA omega-3 during three mo together with a hypocaloric diet which follows the World Health Organization (WHO) recommendations (D+O3), or to receive daily a capsule with 1.0 g sunflower oil and a similar diet (P+D). After randomization, dietary information (24h-recall and FFQ), anthropometric measurements, and peripheral blood samples, will be obtained. Blood samples will be used to determine fasting plasma glucose and insulin, and erythrocytes fatty acid profile; such determinations will be repeated at three and six mo of follow-up. Anthropometry and 24 h-recalls will be repeated monthly. For follow-up, studied subjects will be evaluated monthly to deliver capsules and to check for dietary adherence. Treatments will be administered during three months and the follow-up will continue throughout six months. At the end of the follow-up it is expect that the D+O3 group will present: a) higher decreases in mean weight and body mass index (BMI), b) greater decreases in the mean fasting insulin concentration, homeostasis model assessment (HOMA) index, and IR frequency, c) longer duration of weight lost. Statistical analyses: Student and paired-t test will be used for inter and intra group comparisons respectively. Logistic regression models and repeated measures analyses will be conducted to evaluate the effect of treatments, adjusting by diet and weight loss, as well as by confounders such as puberty and treatment adherence. Infrastructure: The Unit of Research in Medical Nutrition owes the equipment needed to conduct the laboratory determinations proposed in this research, as well as the personnel qualified to conduct, monitor, analyze and evaluate data from field investigation, specially that related to obesity and IR.