When Fat is a Feminist Issue was first published nearly 40 years ago, the response was instant. “Shocking, invigorating,” psychotherapist and author Susie Orbach remembers, from her office. We can see Sigmund Freud’s house from her window. The sense of peace and joy is huge, I note ruefully, because I don’t know whether it’s the psychoanalytical neck of the woods, the yellow furniture, or the fact that it is so tidy. “I had letters from women who were reading Woman’s Own, it went cross-class, which was obviously what I wanted. It got reprinted immediately, it was fantastic. A real sense of: ‘OK, we’re not going to do this any more.’”

What was the “this”? Obsessive dieting and self-hate, compulsive eating and body dysmorphia – all the handcuffs women placed on themselves and assumed, Houdini-like, they had to escape on their own. We weren’t just weak-minded, greedy, ill-disciplined; there were specific realities to the conditions of both fat and thin that we were all chasing or escaping through our eating. Being fat was a protection against sexual attention, but also against being marketed to, having one’s body appropriated as a commercial space. Fat was a statement of solidity in the face of motherhood. It was a defence against competition, a way to dance around the painful establishment of hierarchy within your own gender. Fat meant so much more than calories in and calories out. As did thin, which carried its own freight: that you would be seen as superior and cold; that you would be overcome by your own promiscuity; that you would be perceived as selfish; that there would be no buffer between you and the world.

I remember, in the 80s, a phase of knowing about the book before I’d read it – nuggets of half-processed insights passed like contraband through a single-sex school full of anorexics. “You have to fill your cupboards with forbidden foods. You have to go around a supermarket and deliberately buy things you don’t allow yourself.” And thinking … but then I would have a houseful of bagels, and what could possibly be feminist about that? (If you go the whole hog and read the book, it will explain: “One woman we worked with was persuaded to keep enough ingredients for 75 ice-cream sundaes with all the trimmings … She exclaimed: ‘But I’ll eat it all!’ The idea seemed so sinful to her. It was pointed out that if she had enough supplies for a minor army and could prove to herself that she did not want to consume it all at once, she would feel much more powerful and more in control of her food.”)

This is a truly tragic thing: those vast insights – which ranged from the most profound drivers of problem-eating to the most achievable, real-time routes out of it – changed nothing. Public health still talks about obesity as a lifestyle or ignorance issue, an information deficit – people who don’t know about calories accidentally eating too many of them. The standards to which women are held are more extreme and more distant than ever. Bodies communicate more about status than they ever have and, as that conduit, are the site of more anxiety.

“People used to know they had problems with their bodies and their eating, and they would come for help,” Orbach says, her pessimism always belied by the magnetic atmosphere of reassurance, optimism and challenge she creates when she talks to you. “Now it’s just taken for granted. This is just part of how I have to live – feeling shit about my body, scared of food, either managing it this way or managing it that way. [People who come to see me are] not familiar with feminist ideas, they’re not familiar with anti-dieting ideas, they’re not familiar with the idea that you could actually have a personal solution to your body that doesn’t involve being obsessed by it. When I first started, not every woman had an eating issue; not everybody had a body dysmorphic problem. Now everybody does, but they don’t bother to talk about it. It’s beyond depressing. It’s hateful, really, what the culture has done.”

The political class won’t learn. “I’ve spent so much time talking to governments. There was the body-image summit with the Labour government in 2000, then the Daily Mail accused it of being the nanny state, and they just collapsed. With the coalition, we had a fantastic time. We did some work with new mums so they could feel safe with their babies and not pass on their own eating problems. But that, of course, has stalled with this government, because it’s just not interested.”

Of the cultural surprises delivered by the past four decades, few have been pleasant for Orbach. “I wouldn’t have predicted the international dimension. I wouldn’t have thought that you’d be going to China and seeing billboards of western women projecting that fey, fuck-me look, selling back to the Chinese the clothes that were made in their factories. It’s a form of imperialism, isn’t it? We’re exporting body hatred all around the world. That’s something I did not expect. And I suppose I hadn’t really anticipated the explosion of non-food foods – the chemicals, the sugars that don’t get metabolised by the body.”

It is fascinating to consider the new context for Fat is a Feminist Issue to be reissued: one in which feminism has been through the trough of the apolitical 90s but, if not peaked, certainly resurfaced. That’s positive, of course; it’s less thrilling to find that debates that, in the 70s, were fairly sophisticated are having to start from scratch.

“Feminism,” Orbach recalls, “was a very broad church. There were the women who were going after changing the law and fighting so you could get a mortgage, then there were the women who wanted to get into the banks. Then there were the revolutionary feminists, the radical feminists, the lesbian separatist feminists. Within the grouping that wanted equality in the workplace, we would have been arguing that it would be hard to achieve that on the terms that the workplace is structured. Most women don’t want to be working from seven in the morning until 11 at night. There was a feminist critique of that model. But neoliberalism took hold, and solidarity with other women got turned into a thing called ‘networking’, and that turned into the glass ceiling. It wasn’t meant to be that. It was about: ‘How do we change the workplace?’”

Orbach is often reluctant to make large generalisations of gender, while at the same time irresistibly drawn to the density of pressures and signals that make up its social construction. And yet, she persists. Last week, she broadcast In Therapy on Radio Four, five short programmes in which a different actor each day arrived on the couch for an unscripted conversation. Orbach is immovable in her faith in the mind. “A couple of Fridays ago, I was giving a talk at the Wellcome Collection. I arrived and there were 5,000 people queueing. They weren’t queueing for me, let me be clear. They just wanted to be exposed to sophisticated ideas. They are rejecting oversimplification – they want more texture in their lives.”