The environment of children has drastically changed in Europe during the last decades as reflected in unhealthy dietary habits and a sedentary lifestyle. Nutrition obviously plays a part in the development of overweight and obesity in childhood. However, dietary factors and physical activity are also involved in the development of metabolic syndrome, diabetes, cardiovascular diseases, osteoporosis, and postural deformities like scoliosis. To stop the resulting epidemic of diet- and lifestyle-induced morbidity, efficient evidence-based approaches are needed. These issues are the focus of IDEFICS (Identification and prevention of dietary- and lifestyle-induced health effects in children and infants), an Integrated Project within the 6th framework program of the European Commission. The IDEFICS consortium comprises 24 research centers and small or medium enterprises across Europe. One part of IDEFICS will investigate the etiology of selected diet- and lifestyle-related diseases in 2- to 10-year-old children. The impact of sensory perception and other internal and external triggers of children's food choices and consumer behavior will be studied in this context. Another part of IDEFICS will develop and evaluate strategies for the primary prevention of diet- and lifestyle-related diseases. The results of the project shall contribute to the development of harmonized European guidelines on diet and lifestyle for health promotion and disease prevention in children.