I've read that wheat, a high calorie food, was mainly for the higher classes. Potatoes are high in calories but were only introduced in the 15th century.

I've gathered they mainly ate vegetables and not much meat.

However, to get 2,500 calories (daily caloric requirement for a male) you would need to eat something like 4 whole heads of cabbages and 3kg of carrots. That's an incredible amount of food which I'm pretty sure they wouldn't have access to every day.