'Some do coke. Others do ciggies instead of eating'... Who do you mean, Beth?

The singer insists that, though fat, she is not unhealthy, and challenges the belief that skinny people are healthier.

Beth Ditto, the larger- than-life lead singer of the Gossip, has charged into battle with her size-challenged sisters. Forced to defend her weight once too often, Ditto cracked last week and launched an attack on the conventional belief that it is healthier to be thin.

Although she is several belt notches bigger than the average, size-16, British woman, this is no reason to believe she is unhealthy, Ditto declared. Her ample size-28 frame puts her firmly in the red danger zone of a body-mass-index chart, but Ditto insisted: "I'm not an unhealthy person and... one of the most tiring parts of being fat and being proud of it is... you do a lot of proving yourself all the time."

She added: "It's really interesting to me that people will look at a thin person and go, 'That's a healthy person'. I want to go: 'Come, open my refrigerator and look, and then let's talk about what you think is so bad.' To be thin and to stay really thin... some people literally do coke all the time. Some people smoke cigarettes instead of eating. That's crazy. But that's OK, because you look healthier."

And looking healthier is not enough, doctors have found. MRI body scans have shown that even thin people can have major internal fat deposits surrounding vital organs such as the heart, liver or pancreas. The most vulnerable are those who starve themselves thin because a look in the mirror convinces them they are healthy. Some doctors fear that being fat inside is just as dangerous as the more obvious external fat covering Ditto.

The Gossip singer's tirade, captured in an interview with the broadcaster Fearne Cotton, went right to the heart of the size-zero controversy that has dogged the fashion world in recent years. Campaigners, worried about the toll that being slim takes on models' bodies, have tried to persuade designers to avoid anyone who looks dangerously thin. But with even Mark Fast, the Canadian who kicked up a storm by using plus-sized models a year ago, having only one larger woman in his show last week, it is clear that the skinny aesthetic still dominates. Not that there isn't a demand for larger sizes. The launch of Ditto's second collection for Evans, the plus-sized retailer, last week prompted a global frenzy for her designs from so-called fatshionistas.

The skinny woman's view

Kate Moss The stick-thin model, who was snapped wearing the tiniest of leather hot pants last week, will never live down her admission that one of her personal mottoes was "Nothing tastes as good as skinny feels".

The starver's view

Elizabeth Hurley The actress wrote in a tweet earlier this summer that she broke every nutritional rule in the book by never eating breakfast. "Woken up to sunshine and lots of my best friends. Watching them eat pain au chocolat. Me drinking hot water," she tweeted.

The eater's view

Ashley Greene The Twilight actress spoke for many when she said recently: "A lot of people like to be super-tiny, but I don't want a child's body – I want a woman's body that is extremely fit. It's so much sexier. I'm a big believer in feeding your body what it needs. Deny yourself something and you're going to end up shoving your face full of it."