Obesity has a major impact on the development of cardiovascular disease and other related conditions and it is of particular concern in children. The prevalence of childhood overweight and obesity in Spain is among the highest in the European continent. Childhood obesity has been associated with diseases that were thought to apply only to adults, such as the metabolic syndrome. Insulin resistance is the most important risk factor in subjects with severe obesity, which together with visceral obesity, exacerbates postprandial triglyceridemia, increasing cardiovascular risk.

In this context, the investigators hypothesize that the postprandial lipid metabolism is also impaired in obese pre-adolescents, as it is in obese adults. This includes not only exacerbated postprandial triglyceridemia, but also impaired levels of inflammation markers. In addition, the investigators hypothesize that the lipid and protein composition of postprandial chylomicrons and chylomicron remnants are also altered in obese children when compared with their normal-weight counterparts, and that these postprandial lipoproteins induce foam cell formation differently. The investigators also believe that a Mediterranean-style meal can help to normalize the altered postprandial lipid metabolism in obese adolescents.

Excess of body weight has led the World Health Organization to call it a global epidemic. Obesity has a major impact on the development of cardiovascular disease and other related conditions and it is of particular concern in children.

The prevalence of childhood overweight and obesity in Spain is among the highest in the European continent. The health consequences of obesity in children are not as evident as in adults, but childhood obesity has been associated with diseases that were thought to apply only to adults, such as the metabolic syndrome. Insulin resistance is the most important risk factor in subjects with severe obesity, which together with visceral obesity, exacerbates postprandial triglyceridemia, increasing cardiovascular risk.

However, this has not been appropriately studied in children for the moment. The excellent results of previous projects carried out by our research group have shown the beneficial properties of olive oil on health, being the main ingredient of the Mediterranean Diet, including an improved postprandial lipid pattern.

In this context, our hypothesis is that the postprandial lipid metabolism is also impaired in obese pre-adolescents, as it is in obese adults. This includes not only exacerbated postprandial triglyceridemia, but also impaired levels of inflammation markers. In addition, we hypothesize that the lipid and protein composition of postprandial chylomicrons and chylomicron remnants are also altered in obese children when compared with their normal-weight counterparts, and that these postprandial lipoproteins induce foam cell formation differently, as well as a different release of inflammation markers by macrophages. However, it is also part of our hypothesis, that a Mediterranean-style meal,administrated as a breakfast can help to normalize the altered postprandial lipid metabolism in obese children.

With this aim, we will carry out a dietary intervention study with a randomized, crossover design in a single meal, in order to measure changes in the postprandial lipid metabolism in pre-adolescents and adults affected by obesity and to compare the effect of a Mediterranean-style breakfast. Chylomicron remnants will be isolated from blood serum and will be fully characterized. These particles will be incubated with monocyte cell lines to determine their effect on cellular lipid metabolism and the production of inflammatory factors. In addition, the influence of obesity in the composition and structure of the plasma membrane will also be assessed. The results will generate knowledge about the pathophysiology of obesity in children and will contribute to the dietary recommendations for weight maintenance in this population. Furthermore, it will provide information on the development of atherosclerosis during the postprandial period, which may begin at very young ages.

Inclusion Criteria:

• Adolescents below 15 years-old with BMI ≥ 30 and above the 95 percentile for their gender and age.
• No history of psychiatric or organic disease, except for obesity.
• Appropriate cultural level to understand the study.
• A written informed consent of their parents or tutors.

Exclusion Criteria:

• Subjects being treated with drugs for any kind of disease.
• Those suffering of chronic diseases.
• A negative to participate in the study from them or their parents or tutors.
• Subjects having participated in another clinical study the preceding 3 months.