Children's diets should be greatly improved according to new findings. Children are storing up potential health problems by eating a diet dominated by junk food and other nutritionally poor foods such as snacks, according to a government survey.Experts warn that such an unhealthy diet could lead to increased risk of cancer and coronary heart disease. Four out of five children aged four to 18 regularly eat snack foods such as chips, biscuits and chocolate.The National Diet and Nutrition Survey of Young People found one-in-five of those asked ate no fruit at all during the week-long study.The research, published by the Department of Health and the Food Standards Agency, also found that most young people aged seven and over were "inactive" - and that girls were even less active than boys.The study of 1,700 young people also found that their intake of salt was too high, often twice the recommended levels. Such high sodium diets may be linked to heart problems in later life.Children also consumed too many vitamin and mineral supplements, whilst those from low socio-economic groups had the lowest intakes of energy, fat, vitamins and minerals.However, no evidence was found of widespread malnutrition among youngsters, although trends towards poorer diets are worrying nutritionists.Children should be encouraged to walk or cycle to school to help keep them active and cut the risks of heart disease and obesity in later life.The survey also found: