The army said its new meatless Mondays are meant to cut its consumption of ecologically unfriendly foods whose production contributes heavily to global warming.
"It's a step to protect our climate. The idea is to serve food that's respectful of the environment," spokesman Eystein Kvarving told AFP.
The diet has already been introduced at one of Norway's main bases and will soon be rolled out to all units, including those serving overseas, said the army, estimating it would cut its meat consumption by 150 tonnes per year.
"It's not about saving money," said Kvarving. "It's about being more concerned for our climate, more ecologically friendly and also healthier."
A Norwegian environmental group that campaigns for meatless Mondays nationwide, The Future in Our Hands, welcomed the army announcement.
"The defence ministry deserves a lot of praise because it's taking climate and environmental issues seriously," said the group's director, Arild Hermstad.
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According to the organisation, the average Norwegian eats more than 1,200 animals over the course of their life, including 1,147 chickens, 22 sheep, six cattle and 2.6 deer.
Livestock farming accounts for 18 percent of greenhouse gas emissions worldwide, according to the UN Food and Agriculture Organisation.