Sister act: authors Sophie (left) and Audrey Boss were both overeaters until they learnt how to form a healthy relationship with food

Exhausted by endless dieting and sick of putting on weight, Sophie and Audrey Boss began exploring their relationship with food. Their new book is the answer to an over-eater's prayers

Sophie and Audrey Boss are sisters who each struggled with yo-yo dieting throughout their youth. Together, they devised a way to maintain a healthy weight without diets, and for more than a decade have been running workshops to help free others from the cycle of perpetual dieting.

Sophie: I didn't acknowledge anything needed to change until my early thirties, because until then I'd been on a constant cycle of dieting to try to lose weight and then over-eating in various ways, which I just thought was normal and what everyone did.

I remember going on my first diet when I was 13. I was at boarding school and a friend and I decided we would eat All-Bran for breakfast and two Ryvitas with Marmite for lunch and dinner. I didn't stick to the diet, though my friend did. By teatime I was gorging on bread or anything I could find, in secret so she wouldn't find out. That was when I began to think of food differently and became conscious of it.

There were times in my life when I managed very restrictive dieting and managed to eat incredibly little for a long time and lost a lot of weight very quickly. Most of the time I'd manage it for a while and then I'd get bored or crave the stuff that I wasn't allowed and so I'd cheat before promising I'd go back to dieting again.

At the time, I didn't really feel it was a problem. I shared the common view, which is to get a grip, just stick to the diet and use more willpower. But I realised the more I dieted, the more I over-ate when I stopped, and the overeating got progressively worse. I would buy things I never normally ate such as large packs of Kit Kats and caramels. I'd scour the shelf for anything to make up for that sense of deprivation, all the time persuading myself that this was temporary and I was going to diet again very soon. Officially I didn't eat meat, because my husband is vegetarian, but I found myself stuffing myself full of salami on the way home from the supermarket. I was baking cakes out of boredom and eating them. I was eating because I was going to go on a diet.

The final straw came after I started a new diet because I wanted to go on holiday looking slim. It was supposed to be for six weeks but I gave up one morning early on, knowing I would never see it through. I fell back into over-eating and went on holiday fatter than I had been before I decided to go on the diet because, with that sense of hopelessness, I just ate and ate.

Then I went to visit Audrey in Italy and she showed me a book about compulsive eating, and although my first reaction was, 'I'm not a compulsive eater,' I read it and it was a revelation. Here was a book saying that it didn't need to be like that, that over-eating was something that you could learn to manage, and dieting made it worse. You don't have to eat when you're bored or frustrated or pissed off. The hard thing was to try to let go of my focus being on weight loss. That's harder to do than to say. To address your relationship with food is very hard.

Our book, Beyond Temptation, is about looking at your over-eating and working out why we do it, how we do it, and finding a way to stop that's manageable and sustainable. Most people, organisations, diets and doctors just say stop doing it, stop over-eating. What they don't look at is why you are doing it. What we've realised is that it is incredibly complex. There is a huge variety of reasons why people over-eat – psychological, physiological, emotional – and unless someone is willing to be curious and explore themselves as an individual, rather than think there is some sort of blanket answer out there, then they stand little hope of finding a solution.

Audrey: Growing up, I was very aware of dieting; my mother was always on one and Sophie, who is five years older than me, started young. When I was 11, my mum started a new diet before summer and asked me to join her. She was concerned with my weight but, looking back at pictures, it was obviously just puppy fat. She stood me in front of the mirror and said, "Do you really want to go to the beach looking like that this summer?"

I lost lots of weight and went on holiday very skinny. I realised I could get by on very little so I sort of stopped eating for the summer. Being young, I didn't have that emotional attachment to food that I would go on to develop later. My family told me how wonderful I looked and I loved the attention; it was exciting. Then school started, I went back to eating like before, and put weight on. I spent the next 15 years trying to lose weight.

I'd do extreme diets and fail at them. I even went to the doctor's for slimming pills, which I took for six months while barely eating, before giving them up when I discovered that they were actually amphetamines. Then in my early twenties I discovered that the best way to keep my weight stable was to over-eat and then vomit afterwards.

By my mid-twenties pretty much every meal I had ended up in the loo. In the evenings I'd go to the petrol station and buy every sweet, cake and biscuit and eat them at home. There was a lot of secret eating and purging going on.

By the time I started reading up on compulsive eating, I knew I needed to address my issues. I decided to get some counselling and went to see a therapist. (By then, I'd had a saliva gland taken out because it had calcified and the doctor told me that if I didn't stop what I was doing it would kill me).

In my first session, the therapist asked me why I was there. I said for two reasons: I'm stuck in a really destructive relationship, and I'm vomiting three times a day. She just replied, "That's great, they're both the same thing so we're going to solve them very quickly." She told me the vomiting was the symptom of some unease that was going on and to continue until I learnt how to manage whatever it was I wasn't managing. She would ask me a lot about how I did it, what I ate, how it felt. I spent the next eight months exploring my issues with food and really talking about it with Sophie.

Sophie trained as a psychotherapist, we took courses, and read. We ran groups and workshops and spoke to more and more women. What we found was that everybody was saying the same thing. All these women – of different ages, weights, backgrounds, social groups – all with different experiences, yet all saying that they were sick and tired of being so obsessed and out of control around food. And now we're able to help other women. Nobody should think they are alone in this.

Interviews by Gillian Orr

'Beyond Temptation: How to Stop Overeating and Feel Normal and in Control Around Food' by Sophie and Audrey Boss (Piatkus, £12.99).For more informationon on workshops, go to beyond workshops/ beyond -temptation/

Beyond Temptation: Tips to stop over-eating and feel normal and in control around food

Don't use willpower: Traditional diet advice urges women to rely on willpower and deprivation to stop over-eating, neither of which works in the long term. We don't over-eat because we are weak and greedy. Over-eating is often a coping mechanism like many others and as such it has a positive function. It helps to manage situations, feelings and life in general. How does food help you to manage life?

Be curious: Awareness is the best way to stop over-eating. Observe yourself with curiosity: over-eat mindfully and identify your triggers; find out all the reasons/situations/foods that lead you to over-eat. The more you know about your eating habits, the more information you have to start making changes.

Tune in: Next time you over-eat, tune in. Give yourself a moment to focus on your thoughts, your feelings and what you are doing with your body. How do you talk yourself into over-eating? Discover the thought process that leads you to the biscuit tin. Name and acknowledge the feelings that you eat to deal with or to avoid. What do you do with your body when you over-eat? Scan your body and notice what you are doing with the different parts of your body. What kind of food do you over-eat? Is there a pattern?

Slow burn: It takes time and commitment to make changes to our eating habits. Find a way of supporting yourself. Talk about your experiences with like-minded people and exchange ideas. Being part of a supportive group or community is the best way to make long-lasting changes.