Age rage: My mid-life crisis

It's shocking when you suddenly realise you're middle-aged. But life really can begin at 40, says Danielle Demetriou

A face-lift, a Porsche, a mistress, an extreme sports habit: the mid-life crisis manifests itself in mysterious ways. Few are untouched by the angst that accompanies no longer being young. And among today's high-achieving young professionals, the "mid-life" crisis is setting its claws into men and women as early as their late twenties.

For the MP Mark Oaten, it was going bald that apparently triggered an affair with an indiscreet male prostitute. But in many cases, the crisis is caused by the lucid recognition that long-held dreams may never be fulfilled.

"Men and women spend years carving their places in the world, developing families and careers," says Simon Biggs, a professor of gerontology at King's College London, "but at some stage they begin to think 'I'm coming up to 40 or 50 and what am I going to do with my life?' They begin to see the first part of life as an expansion of social conformity, with work and family life distorting the personality."

But for Mark Oaten and others in the throes of a mid-life crisis, it may be comforting to learn that it often leads to a positive outcome. "Eventually, you realise there's not so much time left - and instead of looking back, you start looking forward," says Professor Biggs. "It is viewed, ultimately, as a positive transformation."

New Career: 'Part of me felt liberated. But I was petrified'

Paul Southern, 44, switched from successful salesman to garden designer following a period questioning his life.

"When I left school, the promise of a company car and a good salary led me straight into sales. Over the years, I was promoted several times, but I was working horrific hours. It tired me out and limited my social life to weekends. As I approached 40 I began thinking about changing my life.

I had always loved gardens. I watched gardening programmes and at weekends visited gardens around the country. I started to think maybe I could do this. I had lots of sleepless nights and eventually decided to take time out, and went to Spain. It was at the Alhambra in Granada that it hit me. I remember thinking how calm and serene it was - and I was convinced I should become a garden designer.

Part of me felt liberated but I also felt petrified. For 16 years I'd had a company car, and a pay cheque every month. Suddenly, I was studying and working on Saturdays in a garden centre. After a year, I set up my business.

It was a steep learning curve but the last few years have been very, very happy. My Alhambra moment has paid off."

PS Gardens (020 8989 2018, www.psgardens.com)

New Outlook: 'His death made me feel I had to take chances'

Bereavement prompted Sarah Strachan, 41, from Maidenhead, to change her world.

I'd been working in IT and living the corporate lifestyle for 12 years and was quite happy. Then, three and a half years ago, my ex-husband died suddenly and it devastated me. I went through all the usual grieving processes of feeling depressed and not knowing where to go with my life. His death made me feel that life is too short and you've got to take chances when you can.

A few months later, a redundancy programme began at work. I decided to take a career break.

I wanted to improve my skiing, so I went to Morzine in France for the season. I skied every day and improved beyond recognition, I did quite a lot of instructor training and even went on a tandem ski-dive. It was great fun meeting all sorts of people; ski bums, chalet workers, instructors. You form some very intense friendships.

While there I started writing a novel, which, again, is risky. The chances of getting published are minimal. It's about relationships and friendships, with a bit of raunchiness. I'm also planning to buy a motorbike; I've got thoughts of taking off around the world, or doing dive-master training in Thailand, or trekking round South America - why not?

New Sexuality: 'I was depressed so much I could hardly walk'

Carl Marshall, 46, from Birmingham, realised he was gay.

Coming out was like suddenly getting my adolescence back at the age of 42. But having been in a marriage that lasted 20 years, the revelation was very painful.

My life had followed a very traditional path. I met my wife at school, fell very much in love, got married and had a daughter. I knew that I felt an occasional attraction to guys, but I didn't recognise those feelings as being gay. When we married, my wife was my soulmate, but, slowly our relationship changed.I started feeling very lonely.

I was irritable, spent a lot of time on my own and couldn't shake the guilt that, underneath, our marriage wasn't strictly honest. I was frightened about my flirtations with other men, and at one point became depressed to the point where I could hardly walk. That was the catalyst.

When I told my wife, it was a huge relief. We tried to stay together, but as time went on I needed to explore my sexuality, and I couldn't do it while we were together, so I moved out. I started to discover the gay scene and joined lots of clubs, communities and organisations. The biggest change is that I'm more self- confident; I don't feel I'm hiding anything any more.

New Body: 'The only fancy dress to fit was a Christmas tree'

Sue Bentley, 41, from Preston, decided to lose weight as her 40th birthday loomed.

My weight had been a problem for years but it was something I learned to live with. I was a busy wife and mother of four and was always occupied with other things. But the turning point came when I was approaching 40. I realised that something was wrong . I was simply very unhappy. I weighed 17 stone and was wearing size 20 to 22 dresses. I remember having to go to a fancy dress do for my husband's work and I went as a Christmas tree. It was the only thing that fitted.

Things reached crisis point was when I realised my health was affected. I'd always been very athletic when I was younger but I was having trouble with my knees and legs. I was worried about ageing and the health problems that might develop. I felt strongly that I was just too young for this and I knew I needed to change.

For 18 months I ate a very healthy diet with the help of WeightWatchers and exercised by running and going to the gym, and I lost five stone. A landmark moment was when I managed to run 1.5 miles in 12 minutes - something I hadn't done since I was 19. But the biggest difference is that I finally feel happy with my life.