**1. Introduction**

Childhood obesity represents the most relevant nutritional disorder in our environment [1, 2]. It usually initiates at early stages in life, when child feeding depends—almost exclusively—on feeding habits and preferences in a family setting; it is subsequently exacerbated (by the time of school attendance and/or adolescence), probably in relation to the adoption of unhealthy feeding habits and lifestyle [3, 4].


WC, waist circumference; BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; HDLchol, high-density lipoprotein cholesterol; OGTT, oral glucose tolerance test.

**Table 1.** Criteria for the diagnosis of the pediatric metabolic syndrome (all definitions considered a child as having the metabolic syndrome when three or more of the following characteristics were present).

Additional studies—except for uncommon situations such as endocrine, genetic or metabolic pathologies, which justify excess body weight—are used for the diagnosis and/or early detection of metabolic complications and, particularly, the metabolic syndrome. This syndrome is characterized by a cluster of symptoms associated with obesity, such as insulin resistance, arterial hypertension (HTA) and dyslipidemia, and its interest lies in the high predictive value for cardiovascular disease and type 2 diabetes in adulthood, especially when it is already present in school children and/or adolescents [5–11].

In the pediatric age, there are no clearly defined parameters for its diagnosis, being several different criteria proposed [12–19] (**Table 1**) on the basis of an extrapolation from clinical guides of adult populations: WHO [20], the National Cholesterol Education Program's Adult Treatment Panel III [21], the European Group for the Study of Insulin Resistance [22] and the International Diabetes Federation (IDF) [23]; this would explain the disparity in published data with respect to the applied criteria [12–16]. Even when the International Diabetes Federation (IDF) refers to the inability for diagnosis in school age, epidemiological data allow suspecting that metabolic syndrome or its components are already present at early stages [23–29].

Leptin is an adipocytokine that, in addition to multiple neuroendocrine functions, has a role in the regulation of energy balance as well as in carbohydrate and lipid metabolism and arterial pressure regulation. In this way, many authors have suggested that leptin might be involved in the etiopathogenesis of metabolic syndrome [30–32].

The aim of this work is to determine the prevalence of metabolic syndrome and its relation to serum leptin concentrations in a group of obese pediatric population.
