There were no vegetarians in cold climate because there were no vegetable crops there, so there was little choice but eating meat.

The need for extra energy in cold climate is satisfied by eating more fat, not by extra lean meat.

Traditionally that was animal fat, but while there are some bad vegetable fat sources there are also vegetable fat sources that are better than the animal fat sources, e.g. olive oil or high oleic sunflower oil or avocado or various kinds of nuts that are high in oleic acid, for example cashews, almonds, hazelnuts, pistachios, peanuts.

Adding a generous amount of olive oil to food can provide enough energy for the coldest climate at a lower cost than using animal fat, while also being healthier.