Pre-schoolers are being sent to nursery with lunchboxes packed with sweets, chocolate and crisps, according to research.
It suggests that youngsters who eat a lunch provided by their nursery or childminder are more likely to be eating a healthy meal than those who bring food from home.
But it adds that all those who are in childcare for the whole day are likely to be eating at least their five-a-day of fruit and vegetables.
The findings come in a new small-scale report by the Children's Food Trust (CFT), which looked into the food eaten by almost 1,500 youngsters attending nurseries, childminders and daycare in Oldham, Coventry and Suffolk.
It found that more than two-fifths (42%) of those who brought food from home had crisps in their lunchboxes, while 24% had confectionery.
In comparison, fewer than 1% of those who ate a lunch given to them by their nursery or childminder had these types of foods.
The study also found that home-packed lunches were much higher in salt.
It said: "There were several important differences in food consumption between food provided by settings and food brought from home at lunchtime.
"Unsurprisingly, children who brought food from home were more likely to have bread or bread-based items (mainly bread as part of sandwiches), cakes and biscuits and fruit, whilst children having setting-provided food had more main dishes and vegetables.
"Water was the most common drink for children having a setting-provided lunch, whilst other drinks (mainly squash) were more common among children having food from home.
"Main dishes from home consisted mainly of ham and cheese (often as sandwich fillings)."
The study was published to mark the first anniversary of national healthy food guidelines for nurseries, childminders and other childcare providers, which offer advice on providing healthy meals for one to five-year-olds.
Overall, childcarers are generally doing well at meeting these voluntary guidelines, the report said, although their menus need to include a wider range of foods.
The nurseries and childminders which took part in the study are not yet following the guidelines, the CFT said.
Dr Tricia Mucavele, head of the CFT's Eat Better, Start Better programme, said: "Childcare providers tell us they really want to nail this, making sure they're giving children in their care nutritious food which sets them up for a healthy start in life.
"There's lots of good practice out there already and these findings highlight the key areas for improvement, which is exactly why the guidelines are needed."