''A kilo is a kilo is a kilo,'' says the airline's chief executive, Chris Langton, about his new fat tax.

And many agree: 85 per cent of respondents to a Herald online poll this week said overweight people should pay more to fly.

Passengers might pass the flight reading NW magazine, which this week pokes fun at Lara Bingle's ''lumpy tummy'' and the ''junk in the trunk'' of Oscar winner Jennifer Lawrence. ''Don't call me fat!'' bleats a pregnant Kim Kardashian on the cover of Who.

Woman's Day, for good measure, delights in a ''fat fight cat fight'' between Olympian Lisa Curry and TV trainer Michelle Bridges, who recently made a contestant cry on The Biggest Loser by screaming at him to ''either go down man-up road or pussy street''.

Anyone who is overweight or obese could well face similar scorn, regardless of their postal address. New York mayor Michael Bloomberg has vowed to pursue his ban on large sugary drinks, recently ruled invalid by the Supreme Court, warning of a ''public health crisis''. Australia, meanwhile, remains mired in an ''obesity epidemic''.

Some argue the focus on health risks has tipped over into prejudice and discrimination against fat people. Australia has become ''fattist'' or ''fat-phobic'', with obese people reviled or, in extreme cases, viewed as diseased, says Sydney University sociologist Deborah Lupton. ''We are already dealing with a vulnerable population and we are further stigmatising them and humiliating them and making them feel less than citizens,'' she says.

Her book Fat, published last year, examines how stigmatisation of body fat has grown with the increased focus on obesity this century. The pendulum of ''moral panic'' over anorexia in the 1980s and 1990s has swung against obesity, she says.

While we condemn sexism, racism and homophobia, fat people are apparently fair game.

''It goes back centuries to Judeo-Christian beliefs that if you allow temptations of the flesh to overcome your will you are a weak person and an inferior person. It affects smokers these days as well. We have great disdain for people who are seen to invite ill health or disease into their body,'' Lupton says.

The title of the reality show The Biggest Loser, where obese contestants compete to shed the most weight, reinforces a general view of such people as ''losers in life'', she says. The decision by Samoa Air to charge fat people more to fly further ''exacerbates the sense of public humiliation'', she adds.

The airline's policy, which was widely publicised this week, requires passengers to divulge their weight when booking a ticket online. Fares vary depending on the distance flown: from $1 a kilogram on a short domestic route to about $4.16 a kilogram for flights between Samoa and America Samoa.

Langton said a similar policy would apply to flights to and from Australia later this year. He argues the policy helps the airline better cater for the obese by reconfiguring seats to give them more space.

Samoa is often ranked in the top 10 countries by obesity levels. In Australia, about 63 per cent of adults are overweight or obese, according to the Australian Bureau of Statistics. An estimated 25 per cent of children are considered overweight or obese. But Qantas has no plans to introduce passenger weight-based fares, a spokeswoman says.

The total cost of caring for the nation's overweight and obese is more than $56 billion a year, according to a Sydney University study in 2010. The personal toll borne by such people is also significant. Fat people are statistically more likely to live in poverty, earn less or be unemployed, have lower education levels and experience lower living standards, Lupton says.

Obesity has been linked to low self-esteem, guilt and depression. A US study in 2010 found parents were less likely to help overweight offspring buy a car.

Public health campaigns, such as Western Australia's ''Live Lighter'' campaign, on television and online, make fat people ''feel disgusted about their own bodies'', Lupton says.

But Mike Daube, director of the Public Health Advocacy Institute, says such campaigns raise awareness about the significant health risks of obesity, such as type 2 diabetes and cardiovascular disease. Early feedback for the ''Live Lighter'' campaign is positive, according to the Heart Foundation in WA.

''We used to hear in the old days with our campaigns against smoking that we were stigmatising smokers,'' Daube, who is also professor of health policy at Curtin University, says.

''I think it is undoubtedly true that some people who are seriously obese feel a discomfort about that but … if two-thirds of us are overweight or obese then I find it hard to claim there is serious discrimination going on.''

It is difficult to think of many situations where the largest group in society considers itself a victim. Some elements of the nation's overweight and obese population have started pushing their weight around (horrid pun intended).

Groups such as Chub Republic and Aquaporko, a ''fat and fabulous'' synchronised swimming team, are trying to reclaim the word ''fat'', turning it from a source of discrimination to one of empowerment.

Victoria University lecturer Jennifer Lee wrote about Australia's growing ''fat activist'' movement in Overland magazine last year.

''Fat people are sent constant messages that they are wrong, that they need to change, that the world around them is fine and doesn't need to cater for them,'' she wrote.

It was time to acknowledge ''thin privilege'' in the same way society had identified the advantages afforded caucasians, heterosexuals and the wealthy, she argued. ''This is a big fat battle - let's fight.''