It also makes sense that we eat more heavy, carb-wise, in the winter and lighter foods in the summer, with spring and autumn being the transitional periods. Its to sustain our body fat, or move it into the direction of the next season. A lot of body in the summer makes it hotter (undesired; already hot), not much body fat in the winter makes it colder (undesired; already cold).

And it isn't only that. Squirrels even harvest so they got food in winter. We've also learned to maintain foods, such as sushi with rice, or with salt or acid so it wouldn't go rancid. Plus, like I said, there's "winter vegetables" which are high on carbs, low on water.