A Smartie sandwich has prompted the launch of a health campaign targeting young children who live in the county, which has one of the highest childhood obesity rates in the UK.
After a teacher spotted a child tucking into the chocolate and carb-loaded snack, concerns were raised over the state of pupils' packed lunches.
Health authorities in Lincolnshire, where one in three children are considered obese, have now introduced a pilot scheme to 32 schools to improve the nutritional value of students' lunches. The NHS has paid for all reception children to have a free hot school lunch.
Lynne McNiven, a public health consultant for NHS Lincolnshire told Huffington Post UK the initiative was also trying to encourage parents to get into the habit of paying for their children to have hot school lunches instead.
"I understand making up a packed lunch is not easy and takes time and effort. We have evidence showing children who have a good, nutritional lunch behave and concentrate better.
"Not only do we want those eligible for free school meals (FSMs) to take up the opportunities to have these, we will try to encourage parents to provide their children with hot lunches, through the school."
Although McNiven described the Smartie sandwich incident as at the "very far end of the spectrum", she added many children did not get the vital nutrients they needed through fruit and vegetables.
"Every day children are being given sugary drinks or bags of crisps.
"These are OK as a treat once a week but these children are getting them every single day."
Lincolnshire already have a health schools team but McNiven admitted it is "very difficult" for one team to monitor every institution.
"Essentially, it is up to the parents to make sure their child is eating the right food but we will do everything we can to help and advise."
The scheme, which started at the beginning of the Spring term in January will run for 20 days until the middle of February.