Almost 350 children were treated for obesity in HSE hospitals in 2017 and 2018, new figures released under the Freedom of Information Act show.
The HSE's statistics show the number of children who had a principal or additional diagnosis of obesity when they were discharged from statutory hospitals.
199 children fell into this category in 2017, and 145 the following year.
The figures include inpatient and daycase stays only, not emergency department or outpatient cases.
Professor Niall Moyna, from DCU's school of health and human performance, said the figures are alarming - but added there are now a lot more public health initiatives to raise awareness of the issue.
He explained: "We're talking about 350 kids, but really we have to educate the general population... and I think parents are [now] much more aware.
"There is a big, big socio-economic influence on the risk of developing obesity in childhood, and we see it much more prevalent in lower socio-economic groups."
Prof Moyna added: "I don't think this is a problem that's particularly unique to Ireland.
"It's a global problem, not just in the developed world but also in the developing world.
"The problem is that many of these children who are overweight or obese at a young age... they're going to present with chronic condition much, much earlier in life than any previous generation."
Safefood, the food safety promotion board, says that in the short term childhood obesity can cause problems with bone health, breathing difficulties, and psychological and social issues.
In the long term, it can cause cancer, heart disease and diabetes.
