Writer and broadcaster Janet Street-Porter has always prided herself on being a rebel. Her aim now is to shake up assumptions about ageing, as she tells Gabrielle Fagan

IF anyone assumed Janet Street-Porter would allow age to mellow and put a sock in her "abrasive, stroppy, rebellious streak", they'd better think again, because this lady's clearly not for changing.

"I feel pretty much the same as the 16-year-old I once was," declares the 70-year-old writer and Loose Women panellist, renowned for her outspoken views and no-nonsense attitude.

"I never liked fitting in, hated rules and people telling me what to do when I was a teenager and not a lot's changed! I'm perhaps not quite as abrasive as I was, but I'm still more abrasive than most people. Age, in my view, is all in your mind and to be honest, apart from seeing my face first thing in the morning (let's face it, you can't defy gravity!) nothing about me feels 70."

With her glossy red hair and flatteringly youthful outfit - jeans and a loose top - her looks do indeed belie her years, but her focus is on being "grateful I've survived seven-action packed decades with a few wrinkles, but absolutely no regrets", as well as her mission to show people how they too can stay young at heart and in mind. She's supporting WE100, a campaign that aims to prepare society to live 100 healthy years.

"At the end of the day, if you don't allow your mind to age, you're three quarters of the way there in holding back the years. As you get older, caution sets in and it can put you off trying new things because you worry about going out of your comfort zone. It's all too easy to stick to the same food, watch the same TV programmes, and only mix with the friends you've know for years because it feels safe, familiar and comfortable," she warns.

"Please don't think though that I don't know what it's like to love routine. It's been a framework and something I've hung on to over the years while I've gone through changes at work and sometimes at home. Even now, I have to admit I eat the same breakfast every day - avocado on toast - and a full English fry-up at weekends, love walking the same routes in Yorkshire and listen to the Archers as often as I can. But the important thing is routine shouldn't take over your life, or it will shrink and narrow right down, squeeze out any opportunity for challenges, and that's really what will age you."

In the past, Street-Porter's certainly never appeared to flinch from pushing her boundaries, and has done it publicly. As well as an enduring career in television, she's successfully edited national newspaper, The Independent on Sunday, and has taken part in a host of reality shows, from I'm A Celebrity... Get Me Out Of Here! to Celebrity Masterchef and stints 'working' as a nurse and a primary school teacher for various TV shows.

"I'm not frightened about many things, but some of those things were very scary to do - I'm as insecure as the next person, but I manage to hide it well - but I made myself tackle them and totally enjoyed them," she admits.

"None of those things have put me off continuing to challenge myself, so my brain doesn't seize up. In fact, since my 70th birthday last year, I've made a list at the end of every day to check that I've said 'yes' to more things than I've turned down. I resolved when I got to 70 to do the best I could with every day that I have."

True to her word, she recently undertook for the first time a session of aerial yoga - participants hang in a hammock to practise the moves - organised by the WE100 campaign. "I dreaded doing it because it sounded quite terrifying and I worried I might fall, but actually it was exhilarating," she says proudly.

"It's about triumphing over that fear of failure which can creep in and make you set yourself limits physically and mentally. Another way I try to shake things up is once a week cooking something I've never made before. Although that mini-challenge might sound pitiful, research shows most people actually cook the same six dishes every single week. My mother always ate the same food and stuck rigidly to her routine and was a bit of a misery, so she's an example to me of what not to do."

While she says what's on the inside counts, Street-Porter also recognises appearance is key. "I know my face shows my age, but the only way to deal with that is to laugh and talk a lot which makes your face come alive," she advises.

"Frankly, there's no need or excuse for elasticated waists and never changing the shade of lipstick you've worn for years. Over the past year, I've radically changed what I wear in favour of highstreet fashion and a lot of the time people think I'm wearing designer labels. There's loads of lovely loose fitting clothes (maybe bought a size bigger or altered) which are great. The divide about what older women and younger women could wear is long gone thank goodness, with the exception of avoiding anything way above the knee."

She laments the fact that older people aren't acknowledged enough "for the experience and wisdom they've gained over the years", but urges them to realise they can take control and change attitudes. "I have that fundamental thing - a stroppy attitude - which is very useful, and I don't worry about being invisible because generally I think it's hard to ignore me," she says, hooting with laughter.

"I think, in general, though, older people can be a little bit docile and feel they're ignored. It's up to them to change that and realise our age group is a very powerful lobby. There are no rules, of course, but it helps to recognise that age isn't a barrier to anything. I mix with people of all ages - not just my own age group - so I'm open to different views and opinions. I've trained myself not to be nervous of talking to new people at parties, which was something I used to hate. Also, I don't do nostalgia and I look forward, not back, all the time.

"Our generation is the one which has redefined ageing every decade of our years. Being 70 is no longer the start of the end of your life, it's just a stop on the journey, and I want to enjoy every day of it."

Janet Street-Porter is lending her support to WE100, a campaign that aims to prepare society to live 100 healthy years. WE100, a global Merck Consumer Health initiative, hopes to inspire people of all ages to try something new for the first time, and help maintain mental and physical health into old age. Visit facebook.com/WE100UK