OVERWEIGHT people now face a three-year wait to be seen at the country's main obesity clinic.
Professor Donal O'Shea, who heads the unit at St Colmcille's Hospital in Loughlinstown, south Dublin, warned that overweight Irish children may rival America's within a decade.
His warning comes in the wake of a study which found that more than a quarter of adult men are obese -- compared to just 8pc in 1990.
The profile of clinically obese patients attending the adult clinic -- which has a waiting list of 790 patients -- has become younger and heavier.
"If you get to (the age of) five fat, then it is very hard to come back from that," Prof O'Shea, who also provided key advice on the television show 'Operation Transformation', warned.
"At the moment 20pc of our five to 12-year-olds are overweight or obese. In the States that figure is 33pc and we will be at the 33pc level in 10 years if we don't actually have an active prevention programme."
A study of 300 obese patients, which was carried out by Prof O'Shea, found that many were overweight before they reached the age of 10.
Just last week the National Adult Nutrition Survey showed obesity in men has increased three-fold over the past 20 years.
The amount of fruit and vegetables consumed fell far below international standards -- with six out of 10 men taking in far more fat and salt levels than recommended.
There are now around 100,000 adults with grade 3 severe obesity -- with a body mass index (BMI) over 40 -- in the country.
The average man attending the clinic weighs in at 21 stone, while the average woman attending is 18.5 stone.
Last year, the clinic had a referral from a GP for a woman, in her early 40s, who weighed in at close to 46 stone. She was taken from her home by ambulance to the clinic, yet there was no bed available to keep her at the clinic, as all units are only out-patient services.
Prof O'Shea said treating severe obesity through surgery could save lives and money, due to the high costs of medication for illnesses such as diabetes.
Around 400 obesity surgeries -- including stomach stapling, gastric bands and bypasses -- have been carried out in public hospitals in Ireland over the past five years. This compares with a nine-fold increase in five years in the number of weight-loss operations carried out by the NHS in the UK -- with 4,000 operations carried out between 2008-2009.
"People are having to go privately to have this done, and the benefits are so great that you can't blame them, even though they are often ill-prepared for it, and don't understand the changes they will have to make after," Prof O'Shea said.