I am an anorexic. I have anorexia nervosa.

What does that mean? According to some, it means being stick-thin like a model or Hollywood star; perhaps it is attention-seeking or maybe it means choosing to abuse body, mind and spirit all in the pursuit of size 8 jeans. Last week, new research suggested that elevated levels of antibodies attack the chemical messages that control appetite and consequently cause eating disorders. So, being anorexic simply means a loss of appetite caused by an infection! The reality is that having anorexia is like being lost in a black chasm, utterly helpless in the control of an invisible force, so overwhelming that you barely resemble the person you once were - or at least the person you wanted to be.

Anorexia is relentless; the mindset drives you to set standards which are, to the rational person, clearly unattainable. Failure is therefore inevitable. Living within the depths of anorexia is terrifying, confusing and totally beyond reason. Living in recovery is not always much easier.

Contrary to popular belief, anorexia and bulimia are not about food. I can sincerely state that I have never lost my appetite - indeed, part of the illness for me was to feel hunger and deny myself food as punishment. I did not allow myself to eat because I believed I didn't deserve to. Abusing food or depriving oneself of food are symptoms, the consequence of an illness so complex that after a lifetime with it, it is still impossible to fathom.

I have lived with anorexia all my life. I was 30 last month. Even though the obvious physical symptoms did not manifest until I was 13, the damaging thought processes were evident before that. When I was seven years old one of my guinea pigs died. I vividly remember carrying the remaining one round the garden telling her over and over again I was sorry and that I hadn't split them up on purpose. I felt so guilty, so responsible, I could not sleep or eat properly for weeks.

When I was a teenager, and my parents, teachers and friends noticed I was losing weight, it was a whole lot longer before I would acknowledge it. The intensity of my feelings of failure and worthlessness grew. I believed I had no right to be alive and that if my parents really knew me, they wouldn't love me. Nothing made sense. The only place I felt safe, felt real, was when I was with my animals. Fuelled by the need to punish myself and the desire to disappear, I engaged in anorexic behaviours. I had a wide elastic belt I wore with my school uniform and every week I would cut a bit more off it. If I had not lost enough weight the belt would cut into me; if it fitted I would simply cut more off. My weight dropped to five stone and with it came the inevitable lies and secrecy, which increased my self-loathing. At the age of 14 I contemplated suicide; it was only my intense love for my animals, that stopped me.

Throughout my adolescence, followed by four years of hell at Cambridge, my behaviour deteriorated to include induced vomiting, obsessive compulsive disorder, alcohol abuse and self-harm. Anorexia makes you into an incredibly unpleasant person and maintaining relationships was difficult. I felt that I was undeserving of friends and so removed from normal life that I pushed people away.

And with no one to keep an eye on me, the anorexia took total control. Leaving my pony, the last of my beloved pets, the self-hatred intensified. The starvation of my teenage years did not occur again; it was more subtle than that. I believed I deserved to suffer but did not want to cause my family worry. I had to keep the illness secret. I developed a fixed routine regarding food; if I ate anything at all I would induce vomiting afterwards but at home at weekends I ate 'normally' (small amounts but enough to stop anyone asking questions). I continued at university with my days filled with rounds of self-abuse - I was the most ill I had ever been. It is a myth that a person has to be skeletal to be dangerously ill with an eating disorder; absolutely untrue.

In-patient treatment, in 1999, came just in time. After Pete (my pony) died suddenly in 1997, the condition hit me with a strength I had never experienced before. Even after 10 years of anorexia I had no idea it could be so all-consuming. I was physically, emotionally and mentally exhausted - and scared. I was certain that, if I did not receive real help, it would kill me.

Nothing could have prepared me for the fight needed to reach recovery. At times, living with the illness seemed easy by comparison. In hospital I had to allow myself to be broken down into little pieces and rebuilt. Discharge from hospital was so exciting because I genuinely believed I was cured. I understand now that life in recovery is management of the illness. Just as an alcoholic makes the daily decision not to drink, I make the daily decision to stay well.

There are strategies I use to achieve this. For example, I always have a plan so that I know exactly what I'm doing. If I have a structure to the day I know that I am not wasting time (a real source of panic for me) and if I have a productive day the risk of feeling a failure - a trigger that can give the illness strength - is eliminated. Every time a negative thought enters my head I have to counter it with a positive thought or action - anything can help, from saying something positive out loud to cuddling my dogs.

My relationship with food is still difficult. I feel guilty spending money on food and struggle with the idea that I am allowed to eat, especially foods that I would consider treats. I constantly ask my husband if it's OK for me to eat the amount on my plate. Every day in recovery is another day It can be an immense struggle; there are times when allowing the illness to take over seems so appealing because the fight would be finished. But anorexia must not win; I simply cannot let it. I have so much to keep fighting for, I have my exceptional husband, wonderful family and dogs and am finally pursuing my life-long dream of an acting career.

I have anorexia nervosa, I am an anorexic, but that is not all I am.

· Katharine Wealthall's Little Steps - Surviving Anorexia and Bulimia Nervosa (Chipmunka) is published tomorrow