Poland faces the same problem of obesity epidemics as other European countries. Polish contribution to the EU research projects concerning overweight and obesity is a direct consequence of recognition of this problem and scientific activity of Polish researchers. At present time early prevention seems to be the only effective approach to decrease obesity and obesity-related chronic diseases in adulthood. Three studies described here consider early prevention of obesity - by decreasing protein intake in infancy (CHOP and EARNEST study) or by behavioural approach in preschoolers (TOYBOX). The Children's Memorial Health Institute is participating in all these projects as a recruiting centre of the subjects studied and as a central laboratory for the CHOP and EARNEST studies. The CHOP study proved in a randomized trial that high protein intake in infancy increases the risk of obesity. The results of the CHOP studies have already indicated the need for protein reduction in infant formulas. This was reduced to 1.8 g/100kcal in the 2006 EU Directive. The results from the TOYBOX project which was started in 2010 have not yet been published.