Scotland now ranks as the world’s second fattest country, just behind America, with two-thirds of adults classed as overweight or obese.
Researchers at Glasgow University claim the country is facing a far worse public health crisis than previously thought.
Almost 40% of men and women in Britain are obese by the time they reach 60, a study revealed.
The annual cost to the NHS of tackling the obesity epidemic is estimated at about £200million.
Analysis of weight gain over a 14-year period found those aged 60 to 70 had the highest obesity levels, with 38% considered dangerously overweight.
“People are growing fatter later in life,” said Professor Mike Lean, co-author of the study which is to be published in the International Journal of Obesity.
“This is a significant public health concern and heralds real problems in looking after our old people.
“We have a vision of old, frail and elderly people falling over and breaking their hips but the reality is that older people are also getting fatter, and that poses an even bigger problem.”
The study is believed to be the largest analysis of obesity levels in Britain’s elderly population to date.
Researchers compared health data on 122,000 individuals in England and Scotland taken between 1994-96 and 2008-10.
Jackson Carlaw, Scottish Conservative health spokesman, said: “This problem is fast becoming a crisis.
“Personal responsibility is the key. Everyone knows what is good for them and what isn’t, it is a case of making them aware of the very serious consequences that lie in wait for an unhealthy lifestyle.”
A Scottish Government spokeswoman said it was tackling the issue through its three-year Active and Healthy Ageing Plan.
Food producers and retailers are also being encouraged to promote healthy food. “We are committed to creating a healthier Scotland.
“Obesity is a complex issue linked to many lifestyle factors and requires action on many fronts,” she added.