Around half of people in the Republic will be obese by 2030, making it the fattest country in Europe according to research.
Europe as whole is heading for an unprecedented explosion in rates of obesity, according to World Health Organisation (WHO) experts.
But the problem will become most acute in the Republic, where it is predicted being overweight will become almost universal.
In 2030, the proportion of obese and overweight men is projected to rise to 89 per cent, with 85 per cent of women falling into this category.
The forecast puts Irish men are at the top of an "overweight" table of 53 countries, matched only by Uzbekistan.
As far as women are concerned, Bulgaria and Belgium are predicted to have the highest proportion of overweight and obese individuals in 2030.
Almost three-quarters (73 per cent) of men and 63 per cent of women in the UK are expected to be overweight or obese that year, with a third of women categorised as obese.
The so-far unpublished estimates, part of the WHO Modelling Obesity Project, were presented at the European Congress on Obesity in Prague.
"Overweight" is clinically defined by a Body Mass Index (BMI) of 25 to 29.9, and "obese" by a BMI of 30 and above.
For this study, the "overweight" category also included anyone who was obese.
Using these criteria, researchers looked at data from all 53 countries in the WHO European region, to compare recorded and projected figures for 2010 and 2030.
In terms of obesity alone, the estimates show a big jump for women in the Republic, soaring from 23 per cent to 57 per cent.
The proportion of obese Irish men was expected to increase from 26 per cent to 48 per cent while the figure for those either overweight or obese rises from 74 per cent to 89 per cent.
Other countries with projected steep rises in obesity included Greece, Spain, Sweden, Austria, and the Czech Republic.
Dr Laura Webber, from the UK Health Forum in London, who co-led the research, said: "Our study presents a worrying picture of rising obesity across Europe. Policies to reverse this trend are urgently needed. Although there is no 'silver bullet' for tackling the epidemic, governments must do more to restrict unhealthy food marketing and make healthy food more affordable."
While few countries were expected to see stable or decreasing overweight and obesity rates, the Netherlands appeared to be doing better than most.
Fewer than half of Dutch men were predicted to be overweight or obese, and just 8 per cent obese, by 2030 compared with 54 per cent and 10 per cent in 2010.
