Metabolic syndrome and thereby obesity is associated with low-grade systemic inflammation and it is likely that this is also the case in children (Ley et al., 2005). It has also been shown that the gut microbiota is different in obese individuals compared to normal weight individuals and that the microbiota seems to have a role in fat storage (Backhead et al, 2004).

Intervention study with overweight and normal weight school age children. The children will be randomised to receive selected probiotics or a placebo. Fecal and blood samples will be collected, and anthropometric measurements (weight, height, skin folds) will be recorded before and after the intervention. The dynamic of the microbiota of the GI will be monitored by molecular methods. Markers of intestinal inflammation (calprotectin) and permeability will be analysed. Blood samples will be analysed to evaluate how the intervention influence the systemic polarization of the immune response by means of cytokine analyses. Furthermore, blood pressure, blood lipid profile and early markers of metabolic syndrome will be evaluated. Hypotheses This study will examine if overweight in children is associated with a different intestinal microbiota and if a change in microbiota caused by probiotics can modify inflammation and risk factors for the metabolic syndrome.

Inclusion Criteria:

• 12-15 years
• IsoBMI>30

Exclusion Criteria:

• Chronical diseases
• Chronical medication