Some lifts could now be unsafe as manufacturers have failed to adjust their stated capacities in line with soaring obesity rates, experts warn.
Elevators are required to display signs showing the maximum number of people they can carry but these have not been updated for over two decades.
It means they are increasingly at risk of being overloaded even when they are transporting the number of passengers they have supposedly been built for, a conference heard.
Professor Nick Finer, of the International Prader Willi Syndrome Organisation, took photos of 112 lift weight limit signs over 50 years in the UK, France, Germany, Italy, Spain, Austria and Finland.
The lifts had been manufactured by 21 companies between 1970 and 2024.
He found the average weight allowance per person - calculated by dividing the stated maximum load by the stated maximum number of passengers - increased broadly in line with average body weight between 1972 and 2002, rising from around 62kg to 75kg per person.
But companies have used the same limit ever since, despite average weights continuing to rise.
In the mid-1970s the average British man weighed 75kg and a woman 65kg, but that has ballooned to 86kg and 73kg, respectively.
Lifts are increasingly at risk of being overloaded even when they are transporting the number of passengers they have supposedly been built for.
Professor Finer told the European Congress on Obesity, in Istanbul, that US scientists proposed raising the standard to 80kg in the 2020s but it was not widely adopted.
Manufacturers' assumption that each person fills a floor area shaped like a small oval is also outdated as bulging waistlines mean many are now big and round, he added.
He said: 'The failure of lift manufacturers to adapt to rising levels of obesity and body size means that lift capacities are overestimated meaning that journey times are likely to be increased and that safety could be compromised.
'What's more, suggesting more people can fit in a lift than is comfortable is stigmatising people living with obesity.
Professor Finer said train and plane seats and doorways are also poorly sized for the very large.
Some airlines including Southwest in the US now make plus-sized passengers book two seats if they cannot fit comfortably into one.
Air France offers a discount on the second seat if a fat flyer needs two.
Professor Finer added: 'People and individuals living with obesity face severe physical and practical difficulties when using standard lifts because they are limited in capacity - even the door sizes are inadequate.
'But perhaps even more important than that is the stigma that they may experience on entering lifts - a form of everyday weight discrimination.
'There are other issues, which are perhaps more prosaic, and that is the lift simulation design is based on flawed calculations.
'The ability to trance people up floors in a speedy time is impacted if you can only get half the number of people in the lift that you designed them for.
'And lastly, there may be safety issues.
'Some lifts do have cut outs if you exceed the weight limit but not all do and I have already had some people come up to me today to say they know people who have been stuck in lifts where it stopped going because the total weight has been exceeded, even though there were less than the stated number of people in it.'
Professor continued: If somebody living with obesity is already in the lift and four or five people try to get into lift, you can see the looks that they give and, you know, they look up to the plaque [displaying the safe capacity] and so on.
'I just think we need, sadly, to super-size many of the things in life.'
According to the NHS, 30 per cent of adults in England were obese in 2024 - equal to around 16 million people - and 66 per cent were either overweight or obese.
Registered nutritionist Louise Payne said: 'People living with obesity face daily barriers that most of society never has to think about – lift weight restrictions being one of them.
'It's clear public spaces aren't always designed with larger bodies in mind.
'This is not simply an issue of comfort, it's about dignity, accessibility, and inclusion.
'Nobody should feel embarrassed, unsafe, or excluded when using public transport or accessing everyday services.'
Jane DeVille-Almond, president of the British Obesity Society, added: 'We need to accept that society is unlikely to revert to sizes from 50 years ago, and start developing facilities for the 21st century.'