Take a bowl of inflated food prices, add a large dollop of environmental guilt and a squirt of controversy from a television chef. Mix together and turn up the heat: within no time you will have a bubbling pot of debate about where our food should come from.

The prospect of lean times ahead and the shift of environmental issues from niche to mainstream are causing food consumers to re-examine their priorities. After decades where we have enjoyed the fruits of many countries, the pendulum of public opinion appears to be swinging away from imported foodstuffs towards the home-grown variety, and farmers' markets are booming.

Against this backdrop, Gordon Ramsay has been arguing that British restaurants should be fined if they serve fruit and vegetables that are not in season, and that food should be locally sourced. Such moves, he believes, would cut carbon emissions from air freight and lead to improved standards of cooking. "I don't want to see asparagus in the middle of December. I don't want to see strawberries from Kenya in the middle of March. I want to see it home grown," he said in an interview to launch his latest television series.

It's certainly an idea that's gaining popularity. It was also revealed this week that a group of volunteers in Fife who have pledged to eat only local food for an entire year have seen their ranks swell from the original 19 volunteers to more than 300.

Mike Small, a freelance writer from Burntisland, launched the Fife Diet in November 2007 with the slogan Think Global, Eat Local. The idea was to live for a year on food produced, reared or, in the case of fish, landed in the Kingdom of Fife.

While organic is a bonus when it comes to the Fife Diet, the main objective is to support local, traditional food producers. Participants keep in contact and exchange recipes on an online blog. The Fife experiment follows the example of a Canadian couple who, in 2005, created the 100 Mile Diet, which involved eating food sourced within 100 miles of their Vancouver apartment.

But as the debate over Soil Association plans to change its labelling system to include food miles shows, the question of how far a product has travelled is not the only consideration when assessing its environmental impact. The association intends to give food air-freighted to Britain the organic label in future only if it meets high standards relating to Fairtrade and the environment. Some, such as the Cooperative Group, have argued this puts undue focus on air miles while the environmental impact of the domestic meat and dairy industry is hardly scrutinised.

Sam Roger, founder of EthicsGirls, an online fashion shop and forum, started the Fife Diet as a New Year resolution. "I used to work in Fairtrade food in Edinburgh and my dad was a farmer, so I'm really interested in farmers and in local food," explains the 42-year-old, who lives in Rosyth. "I'm treating it like a diet, but a diet for life." Already a regular at farmers' markets, Sam is gradually restricting the origin of her food to a more localised area.

"I get as much as I can from Fife with the aim of getting better in the long term. If I can't find Fife, I'll just go for Scottish - so far I haven't found butter and cheese in Fife. For things that I can't, or won't, cut out, like coffee or fruit, then I try to buy Fairtrade or organic. So I try to make my own ethical decisions. It is very easy to eat totally Scottish."

Like most of the other Fife Dieters, she allows herself salt, pepper and olive oil from outwith the region, as well as soya milk. "I eat a lot of home-made chips but now that the weather is changing I'm craving salads," she says. "It's been quite meat and potato-oriented, and I think it would be difficult for vegetarians. I've rediscovered shepherd's pie and parsnips in mashed potato. But with a family who didn't like everything, it might be quite difficult."

For Sam, the stranglehold of supermarkets in her area was a factor in her decision to take part. "One of the reasons I'm doing this is that I'm really annoyed that we've got no shop choices. We've got two supermarkets, a small local store, a butcher and two bakers: that's it, and Rosyth is quite a big place.

"What I've found is my supermarket shopping has basically gone down to gluten-free bread, cat food and things like toilet roll. I tend to do most of my shopping at the monthly farmers' market in Dunfermline. If I'm visiting friends in Cupar or Auchtermuchty, I'll go and find a farm shop on the way."

Sam says that buying local has been less hassle than she anticipated as she makes an effort not to travel too far. "Things like root vegetables, if they're covered in mud, actually keep, and I shove all my meat in the freezer so it does last. I'd say I spend less time now sourcing food - it becomes easier as you go along, as you discover more places. I now get beautiful beef from a farmer near Aberdour and ice-cream from Culross."

But will it ever catch on with the average shopper? The benefits of Fairtrade and organically grown or reared food have entered the mainstream consumer consciousness in the past decade. Joan McLachlan, owner of the AbFab hair and beauty salon and a mother of two from Newton Mearns, believes she is fairly well versed in the arguments for each.

"I am a vegetarian - or, rather, a pescatarian eats fish but not meat. My first choice is organic. I've been 80% organic for the past four years. The main reason for eating organic is health. I drink organic soya milk and the boys, who are 16 and 21, have organic milk - I won't have anything but organic dairy. They also have organic meat. The cost of organic stuff is coming down as the supermarkets are realising that it's getting more popular. If I can't get organic, I get Fairtrade because of the wages that producers are on."

But, like many consumers, Joan must balance different factors when shopping. "I do try to buy local and seasonal - I love it if there's a farmers' market on somewhere. Sometimes, though, my older boy likes a pineapple or a melon or something, and I'll buy that.

"Cost is important, but if it were a choice between cheap imported food and more expensive local stuff, I'd go for the home-grown. But you definitely need some flexibility. If you're a career woman, working, with your family to look after, you don't have the time to track down entirely local produce. So if you buy organic and take your Bag for Life, you're doing your bit."

While a move towards increased self-sufficiency is generally viewed as a good thing for an island economy such as the UK, there has been criticism of a blanket policy that would penalise third-world producers. Oxfam's head of research, Duncan Green, responded to Gordon Ramsay's comments with a warning. "The million farmers in east Africa who rely on exporting their goods to scrape a living would see Gordon Ramsay's assertions as a recipe for disaster," he said earlier this week.

The whole concept of air miles as a guide to the carbon footprint of a product is now being described as being too simplistic, as it ignores the carbon cost of production and fertilisation.

John Stocks, manager of the Carbon Trust in Scotland, says: "Food miles and the carbon emissions related to transport are only one part of the carbon emissions associated with the production of food and should be considered in conjunction with the total embodied carbon in the life cycle of the product. This is why the Carbon Trust is working with Defra and BSI British Standards to develop a standard that will create a robust way of measuring all the carbon emissions related to a product or service, from the production of the raw materials right through to the use and eventual disposal."

In the mean time, the desire for home-grown food has been reflected in the increase in restaurants specialising in local fare. When ethical eaterie Iglu opened its doors in Edinburgh's New Town three years ago with the ethos "organic, wild and local", it was regarded as pioneering.

"When we first started, there was no-one really talking about this, and we had to sit on the phone, trawl the internet and go and see people," says manager Gus Niven. "It was a hell of a lot of work. I'd like to think that we're now part of a community. It takes someone like Gordon to come along and bang the drum before people start taking notice."

The restaurant buys a mixture of organic and local produce but Gus admits there is often a choice to be made between the two. "Our ethos is organic, wild and local so if we can tick one box, excellent; if we can tick all three, that's amazing. Both organic and local are up there for us."

Iglu's organic vegetables come from Scotland and England. "Our herbs aren't organic but they're from Scotherbs in Perthshire. There are certain producers that are not organic because they don't feel it is necessary to go through the whole three-year organic certification by the Soil Association but care about their animals and don't use pesticides or growth hormones. If it's being produced here, then why not use it here - and if it's in season then you use it. And if not? Well, you just have to be a bit more creative with your root vegetables in winter."