Feeding off my post about what our bodies expect, I thought I'd take it to another dimension. It's a total myth that since humans evolved in the seasonless equator, seasons don't matter. They do have seasons at the equator, they are just different from what we think of as seasons. As discussed in Seasonality and Human Evolution, the seasons we dealt with for most of our evolution were just two: wet and dry.
Neanderthals show physical adaptation to cold climates, but all humans have a fairly "tropical" morphology. That doesn't mean that the northern four seasons are unimportant, especially since the duality is still present and there is the possibility of smaller, but still important, genetic changes. Particularly significant is that genes for energy metabolism show climactic variation.
Either way, no matter where your ancestors came from, eating the same diet all year is probably not natural. Eating with the seasons enables you to adapt better to your environment and to reap the benefits of two types of diets. Paleo dieters already mimic the feast and famine of early life with intermittent fasting, but eating seasonally allows you to also mimic another important duality.
Right now many of my locavore friends are complaining about the lack of food selection in this late winter season. Most of them are vegetarians or eat very little meat and are having to buy imported foods to get by. There are a few stalwarts surviving mostly on various roots and tubers, but that doesn't seem very delicious or nourishing to me.
While they eat their potato beet rutabaga pie, I'm eating luscious chicken confit, beef stew, lamb shanks with celeriac mash, and wild boar with garlic kale. Local doesn't feel forced to me anymore, it's easy and natural.
It took me a long time to get to this point. When I was raw vegan I savored bananas. melons, and salads in the dead of December. Back then, even a teensy draft set me a shivering. I was completely miserable. My diet was full of "live" foods, but I felt dead. No matter how many layers of sweaters and blankets I put on, I was freezing. A walk along the frigid harbors of Stockholm was impossible.
This winter I have eaten ample amounts of fat and thyroid-supporting foods like seaweed. I feel perfectly warm and no longer need five gazillion wool blankets to get to sleep. The cold north wind blowing off the Hudson river doesn't faze me. I hardly feel deprived...I LOVE the food I'm eating and I feel nourished. The best thing is that I no longer crave sweet foods like I used to. I chalk it up to adequate fat.
December used to be for peppermint ice cream, February for gallons of heart shaped candies, and in early March I started my Cadbury Cream Egg binge. Last night I passed the Cream Eggs at the store and was briefly filled with nostalgia....but then I remembered how insipid they taste and how much better my duck confit tasted.
I hesitate to recommend TS Wiley's Lights Out: Sugar, Sleep, and Survival, because I feel it's a little lacking in scientific rigor, but it does have some important ideas. Wiley believes eating sugar in the winter keeps your body in a constant state of summer, where you need to eat as much as possible to pile on pounds for a long winter. Her prescription is to eat no sugar in the winter, but as much as you want in the summer. A similar idea may apply to omega fatty acids-: omega-3s are a summer fat and omega-6s a winter fat according to Susan Allport (hat tip to Matt Metzgar). That makes so much sense to me. The omega-3s in meat come primarily from fresh grass and animals lay down omega-6 rich fat stores for the winter. Omega-3s in large amounts can also have an immunosuppressive effect, which could be maladaptive for a long tough winter. Another area of concern that seems to be seasonal for me is the acid-base balance, which is slightly controversial, but regardless, my diet is net acid in the winter and net alkaline in the summer.
We can't forget the obvious thing: Vitamin D from sunlight, which probably accounts for the seasonality of some of the illnesses in the aforementioned book. Vitamin D is important in the winter, but it's even more important to go outside and get some sunlight in the summer when your body is expecting it.
Despite the richness of my diet and exercising much less in the winter, I have no gained any weight. In the summer I expect that my desire for fat will wane and I'll fully enjoy the bounty of fruit, herbs, and fish at the farmer's market. By autumn, as the days get colder, I will yearn once again for richer foods.
My ancestors have lived in the North for a long time, perhaps this is what my body expects. Either way, eating seasonally has allowed me to feel better and to truly enjoy local food in a way I never did when I forced myself to eat low on the food chain.