This term may originate in a recent report in which it was claimed that supermarkets/restaurants who bought food locally would be more beneficial in terms of the environment than buying organic food from further away that had to be transported.

"The report's authors - Professor Jules Petty and his colleague Tim Lang from City University - say that people should try to buy food from within a 20km (12-mile) radius."

The links lead to further info.

Norsk Landbrukssamvirke also have some info: "Kortreist mat

Av: Hilde Helgesen

Sparer miljøet for utslipp av karbondioksyd
Gir forbrukerne fersk mat og innsyn i produksjonsmetodene
Bidrar til levende lokalsamfunn og kulturlandskap
Mer av verdiskapningen tilbake til bonden og bygda".

I couldn't find an equivalent term in the english links, but this is what it means. Perhaps someone else knows of one.