The focus of the research in this paper was on dietary habits, prediction of the metabolic syndrome and effects of education on health in adolescents aged 14 to 17 years in 3 Croatian regions. The aim of the study was to determine eating habits, anthropometric characteristics and biochemical parameters of blood and to determine the frequency of weight gain, obesity and prediction of metabolic syndrome in participants of different ages and genders in Dalmatia, Eastern and Central Croatia. The other aim was to examine the effects of education on nutrition and healthy lifestyles during a period of one year with respect to the observed parameters. A dietetic method was conducted (non-quantitative questionnaire on the frequency of food and beverage intake), together with anthropometric measurement, blood pressure measurement and biochemical analysis of blood. After the targeted education with regard to the established nutritional habits of the participants was concluded, a second round of determining of dietary habits, anthropometric measurement, measurement of blood pressure and biochemical analysis of the participants' blood was started. Conclusions were drawn on the changes of participants' dietary habits, the frequency of their overweight, obesity, and predictions of metabolic syndrome. The adolescents differ from each other in dietary habits and prediction of metabolic syndrome by: age, gender, and geographical region. The positive effect of education on dietary habits and healthy lifestyles is manifested in significant changes in the dietary habits of the female participants compared to the total number of participants from all regions. After the education, there are no significant changes in the normal diet of participants in both gender from Dalmatia and Central Croatia, while the number of overweight participants from Dalmatia and obese participants from Eastern Croatia is increasing. Before and after education, the prediction of metabolic syndrome was established in one participant from Dalmatia, according to the criteria of the National Cholesterol Education Programs (NCEP). The most common parameters of participants with prediction of metabolic syndrome are high blood pressure and lowered HDL-cholesterol.