Starting this week, one woman living in London is going to try. As a social and personal experiment, Katie Austin, 23, who works for a women's charity, is giving up supermarkets for Lent.

The old Christian custom of denying oneself one of life's necessities or pleasures in the period between Ash Wednesday and Easter Sunday is very much in decline. But Ms Austin, a practising Anglican whose mother is a vicar in Suffolk, and who has previously given up sweets, chocolate and fizzy drinks for the 40 days of Lent, is now going to do the same with Sainsbury's et al.

She has no illusions about how hard it will be. Ms Austin is a keen cook who lives with her partner in Fulham, south-west London. She admits to being dependent on the big supermarket chains, and foresees an awful lot of aggravation in trying to do without them.

She is what she calls "a shopper with a conscience" and can see that the supermarket phenomenon has another side to it besides shoppers' convenience. Ms Austinbelieves in supporting small retailers and local producers, often squeezed to death by the buying power of the supermarket chains, and is keenly aware of other drawbacks, such as the food miles involved in airfreighting produce not in season in Britain from halfway across the world, and consequent environmental damage.

Furthermore, as someone who sympathised with, The Independent's campaign against excessive packaging, she is frequently irritated by the fact that in a supermarket she is sometimes forced to buy four or six of something, rather than the two she wants.

"I'm not saying we shouldn't have supermarkets," Ms Austin said. "There's a need for them. They are convenient.

"But I wouldn't want local producers and retailers to fall by the wayside, either. I'm not perfect by any means, but I try to be a responsible shopper. I always buy British, apples, pears, potatoes, because I think the damage to the environment from food miles is atrocious and something needs to be done about it."

Reactions from family and friends to her ground-breaking Lenten sacrifice have varied. Her mother, the Rev Cathy Austin, assistant vicar of St Peter's Church in Henley, near Ipswich, thought it was a "fantastic" idea. "She knows I like a challenge, and she thought this was in a very good cause," said Ms Austin.

But she added: "My girlfriends thought I was absolutely potty, when I told them. They thought it was impossible. But then when we talked about it, they started to see the advantages. For instance, I won't be buying all the extra things you chuck in your shopping trolley, thinking, I'll have that, that looks nice, that's the reduced rack, this is a four-pack. I'm going to be buying just the food I need, just the bread I need. If I go into a vegetable shop I'm not likely to be tempted by chocolate eggs ..."

Ms Austin lives with her partner Tom Martin, 26, in a rented house shared with another friend. She does the shopping for herself and Mr Martin (who is going to take part in the supermarket-free experiment with her, so she can't cheat through him) and typically spends £70 on a Saturday supermarket shop, either at Sainsbury's in Putney, or Waitrose in Fulham. She then "tops up" with another £30 worth of groceries during the week.

"I'm will have to go to several different shops to buy my weekly groceries rather than buying it all under one roof, and then you have the problem of opening hours," said Ms Austin. "Local shops are going to be open largely in working hours so I'm going to have to use my lunch break rather than go shopping after work."

Another potential problem - being realistic about it - is freshness. "It sounds awful to say this, but there might be some sacrifice of quality in what I buy. Ingredients from supermarkets largely are replaced daily so they're always fresh, whereas in local shops the quality may not be quite so high."

She thinks shopping locally may cost her more, but as she won't be adding impulse buys to the trolley it may even out in the end.

She did her last supermarket shop for six weeks on Saturday. From Wednesday of this week - Ash Wednesday - there will be no more Sainsbury's, M&S, Waitrose, Tesco or any of them until Easter arrives.