If you find yourself asking "where's the beef?" you may have a case of the Mondays. Meatless Monday is an increasingly popular movement in which carnivores cut out meat one day a week for health and environmental reasons.

The campaign started in 2003 as a nonprofit public health initiative of The Monday Campaigns, in association with the Johns Hopkins Bloomberg School of Public Health and the Johns Hopkins Center for a Livable Future in Baltimore, Maryland.

But aside from the alliteration, why meatless and why Monday?

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