One in six schoolchildren are classified as overweight or obese, according to a new national food survey.
However, the levels have stabilised or decreased in recent years - especially in girls.
The prevalence of overweight and obesity is 16% (boys 14%, girls 19%) - which is down from 25% (boys 19%, girls 30%) in 2003/04.
The dietary habits of children aged five to 12 years were examined by a number of universities.
It found that intakes of fruit and vegetables are low, about three servings a day - well below the recommended five to seven servings.
While intakes of sugar, salt and saturated fat are higher than recommended.
Most children are getting sufficient vitamins and minerals - but significant numbers have inadequate intakes of vitamin D, calcium, iron, folate and fibre.
It also found recent drops around the amount intake of milk, fruit juice, sugar and sugar-sweetened drinks and salt consumed.
And the amount of fruit, brown/wholemeal bread and water has increased.
Eating at home is the main source of calories and the main influence on dietary quality for children in this age group.
While the main barriers seen by parents to providing a healthy diet for the child were the child's likes and dislikes, convenience, other people minding the child, and food advertising.
The study was carried out by a team of researchers in University College Cork, Cork Institute of Technology, University College Dublin and Technological University Dublin.
It documented the diet and body weight of a nationally representative sample of 600 children from primary schools throughout Ireland during 2017 and 2018.
The survey included direct body measurements as well as essential information on lifestyle, including physical activity, for the children.
Participation of children in physical activities is relatively high, with an average of 81 minutes per day spent being physical active.
A total of 69% of children met the recommendation of at least 60 minutes per day of activity.
The study also provided up-to-date information to allow the food industry to tailor product development and promotion to support balanced, healthy lifestyles.
Dr Janette Walton, from Cork Institute of Technology, said this data can be used in the development of healthy eating guidelines.
"We need to continue to promote guidelines for healthy eating for this age group - guidelines that focus on appropriate portion sizes, lower consumption of fat, salt and sugar, and higher intake of vegetables and fruit and other foods that provide key vitamins and minerals."
According to Dr Breige McNulty, UCD Institute of Food and Health, the research will assist in the development of programmes to tackle childhood obesity.
"Although we still have high levels of obesity in children, this study shows that overweight and obesity appear to have stabilised or decreased in recent years, especially in girls. The high levels of overweight and obesity in schoolchildren need to be addressed," she said.