Four out of five over-50s are overweight or obese, a study has shown.
Only one fifth of men and women in the age group are classed as having a normal waistline or an acceptable measurement of body fat to height and weight.
The alarming findings, released by the Irish Longitudinal Study on Ageing (Tilda) led by Trinity College Dublin, highlight the increased risks and burden on health services caused by a fatter population.
And it follows a warning earlier in the week from the Royal College of Paediatrics and Child Health that more than a quarter of children in Ireland are obese or overweight.
The problem is becoming so severe that obesity among Irish men over 50 is now on a par with the US, Tilda said.
The report said that Irish women are more at risk from the connection between poverty and weight problems with 39% of women in the lowest wealth bracket classed as obese compared to a quarter in the highest bracket.
Dr Siobhan Leahy, Tilda research fellow, said the study found worryingly high levels of obesity and the impact this has on health and everyday activity.
"While this age group is already more likely to be affected by age-related illness, frailty and cardiovascular disease, these conditions are exacerbated by the presence of obesity and significantly higher levels of disease and disability are evident in obese individuals," she said.
"Our study highlights the combined impact of the obesity crisis and a rapidly ageing population on health and health service demand."
Experts measured both the waistlines of over-50s as well as the ratio of body fat to weight and height - B ody Mass Index (BMI), the most common method of defining obesity - amid concerns the standard obesity rate of plus 30kg/m2 BMI does not reflect how bodies change with age.
The study measured waistlines to identify excess fat with "normal" classed as below 80cm or 32 inches in women and below 94cm or 35inches in men - anything above 88cm or 35inches in women and 102cm or 40inches in men is classed as central obesity and more closely associated with cardiovascular problems.
Tilda said the BMI measurements showed 36% of Irish people over 50 are obese and a further 43% are overweight, while waistline checks showed more than half are "centrally obese".
It also said the BMI reports found more obese men, 38%, than women, 33%.
The report is the first time obesity in the age group has been examined and it also found:
:: Clear links are identified between obesity and physicality in both men and women with obese women walking more than 10cm per second slower than normal.
:: Obese people visit their GP more often, take more medications and a higher proportion report using of five or more medications.
:: The risk of cardiovascular disease is higher - 48% of obese people reported high blood pressure, while 21% of centrally obese men report at least one cardiovascular disease compared to 14% of men with a normal waist circumference. The rates for women are 17% compared to 11%.
:: Other health risks increase with 11% of obese people diagnosed with diabetes and arthritis affecting 44% of obese women.
The study raised concerns about the effect obesity has on the health services and it noted an estimated 1.3 billion euro spend on increased demand for care, work absenteeism and premature death as a result.
Dr Anne Nolan, Tilda research director, said the demands on the health service are a cause for concern.
"A greater focus on health promotion and prevention is required to not only improve population health and well-being, but also to ensure the future sustainability of our health system," she said.
The Tilda study is examining the health of 8,000 people over 50 in Ireland.