A new worldwide study on obesity suggests that by 2025 the level of obesity among women in Ireland will be the second highest in Europe, just behind the UK which will be the most obese.

The research, published in The Lancet medical journal, also found that almost one-fifth of the world's obese adults live in Ireland and five other high-income English-speaking countries - Australia, Canada, New Zealand, the UK and the US.

Overall, the research shows that more adults in the world are now obese than underweight.

Scientists said that four decades ago being underweight was a bigger problem than obesity, while today obesity in men has tripled.

Furthermore, it said that there is almost no chance of meeting a global target to reduce obesity.

The research was conducted by scientists from Imperial College London and compared body mass index among almost 20 million adult men and women from 1975 to 2014.

The chair of the Royal College of Physicians policy group on obesity has said obesity is driving part of the trolley crisis in Ireland.

Speaking on RTÉ’s Morning Ireland, Professor Donal O'Shea said if the matter of public health is not addressed when a new government takes over, it will create an impossible situation in terms of health.

Prof O'Shea said the study should be seen as a reminder to all those in the negotiating room that public health is a key part of the health policy for the next government.

He said over the last 40-50 years Ireland has gone from nearly the thinnest nation in Europe, but a change in diet to high salt and sugar and a decrease in physical activity has changed our weight rapidly.

He described the sugar tax on fizzy drinks as a "single wave of the hand" at the problem and said more needed to be done.

"We do have to use this study as a kind of a wake up call to say 'look, we have to deal with the hospital situation, we have to deal with the GP situation'.

"But if we don't address the obesity epidemic, we're just going to continue feeding cancer into waiting lists, feeding diabetes into waiting lists," he said.