February 16, 2011

Why do we crave carbs when it's cold, and meat when it's warm?

Recently I mentioned that I experimented with a candy bar diet when I got sick and kept from getting worse, even getting better. That was just one episode in a larger trek away from a paleo kind of diet during the winter holidays. I did that last year as well during winter.

I find myself much more likely to want carbs when the weather is really cold, and even if I try to return to a caveman diet, it's incredibly more difficult during the winter than during the spring or summer. For instance, when I had some cupcakes and ice cream at my mother's birthday party a couple summers ago, I bounced right back. In fact, when I first started eating low-carb, it was spring and I took to it without any pain at all.

And it's not just me. We have holidays and festivals scattered throughout the year, yet it's only the ones during cold-weather times when we feel like pigging out on starches and sweets. During hot-weather times, we feel more like feasting on animals and leaving the sweets aside. Most of this is obvious, but if you want to check, just go to Google Trends and search for something like "pie" or "cake" or the generic "sweets," and you'll see that people search the internet for these things much more when the weather is cold and hardly at all when it's warm.

Just to run through the examples, though:

- The first big gorging-on-carbs holiday is Halloween, right at the end of October. It features little or no meat, or even savory vegetables and fresh fruit. Nope, it's all about easily digestible carbs like sugar.

- Then comes Thanksgiving about a month later. Although there is some meat -- it wouldn't be an omnivore's meal without one -- it is dwarfed by the starches and sugars. Out come the buckets of mashed potatoes, cranberry sauce, corn pudding, sweet potato casserole, rolls, and then a seemingly endless train of pies. There is little whole fruit, and not even that many real vegetables -- maybe a token tray of asparagus or brussel sprouts at most. This meal extends all the way through Thanksgiving weekend.

- Next is Christmas, where again there is some meat but mostly a repeat of the Thanksgiving style of dinner, which also lasts for a lot longer than just one meal. In Google trends, "candy" shows two spikes -- one leading up to Halloween and one just before Christmas. Throw in all those candied and chocolate-covered nuts that your relatives send you, plus eggnog, hot chocolate, and apple cider, all of which are consumed during winter broadly.

- Among Jews, Hannukah time is full of the same kind of sweets that everybody else eats (cakes, pastries), starches (potato pancakes), plus chocolate gelt.

- New Year's Eve is like Thanksgiving or Christmas without the big hunk of meat, although food comes in smaller portions.

- Super Bowl Sunday features little meat, aside from some wings (and even these are soaked in sugary sauces). It's mostly about pizza, chips, bean dip, nachos, beer, and soda. It's close to a carbo-voric vegan's dream holiday. "Chinese food" shows a spike in Google Trends during the winter holidays, and I'm sure some of that is Super Bowl-related. (Not due to Chinese New Year, since Chinese Americans would never search the internet for "Chinese food.")

- Valentine's Day is all about sugary sweets.

- Mardi Gras has no standard big helping of meat, and like Valentine's Day is mostly about sweet pastries like the king cake, and candy.

So from roughly November through February, we go into carboholic mode. There aren't any big holidays in March, except St. Patrick's Day, although that has no standard food, and to the extent that it does it's carb-loaded alcoholic drinks. Jews celebrate Passover Seder with a fairly savory and fat-and-protein-rich meal. Even all the stuff made with matzo isn't sweet. There may or may not be a Passover cake. I distinctly remember a Seder dinner with my friend in 8th grade, and it was no starch-and-sweets binge like Hannukah.

- Getting into spring, Easter is neither here nor there. On the one hand, kids eat some Peeps and Cadbury creme eggs, but it's only a little bit and probably nothing much more than they would normally be allowed during the weekend. And on the other hand, the most famous tradition is to decorate and eat a bunch of hard-boiled eggs -- no carbs, lots of fat and protein.

- Spring Break features little sugar or starch, and more animal foods. It's a generic beach meal; see July 4th and other summer festivals.

- In May and June, there's Mother's Day and Father's Day. Why don't we buy them really starchy or sugary foods then? If they were held in January, you can bet we'd send them pies, cakes, cupcakes, candied nuts, cookies, pastries, or something. If food is involved at all, we take them out for dinner, and it's no different from your typical nice dinner out.

- Memorial Day weekend has no special foods, but people haven't turned to it as an excuse to binge on sugar like they have with cold-weather holidays. People usually make something like a light version of Fourth of July food.

- July 4th has very little emphasis on sweets for a holiday. There might be some potato salad and ambrosia, but most of what everyone eats is dead animals -- hot dogs and hamburgers especially, but also steaks, lamb chops, pork chops, and anything else you can throw on the grill.

- New England clambakes, where people gorge on animal foods and not much at all on sweets, are held mostly during the middle half of the year. Same with Midwestern fish boils. And also Hawaiian luaus. In general, summer festivals are all about slaughtering a bunch of animals and setting them on fire.

- Going back to Jews, neither Rosh Hashanah or Yom Kippur features super-starchy or sugary food. Maybe some semi-saccharine fruits for Rosh Hashanah, but no cornucopia of pies, pastries, cakes, etc.

- Labor Day weekend is also like a light version of the Fourth of July. No explosion of pies, cakes, pastries, mashed potatoes, cranberry sauce, or whatever.

- Finally, Oktoberfest, where it is celebrated, takes place in September-October and is very meat-intensive, along with a handful of starch (and beer), with hardly any sweets.

So from roughly March through October, and especially during the summer, we leave carboholic mode and start to chow down on any animal food we can get our hands on. The only exception is that people eat more ice cream and popsicles during the summer, although even that is dwarfed by all the muffins, brownies, cookies, etc. that we wolf down during cold weather.

Clearly this has nothing to do with the availability of these foods here and now. Sweets are available year-round at the same level, and so is meat, thanks to industrialization, refrigeration, etc. Our tastes therefore reflect what adapted us to earlier environments. It's probably not farming life that made us this way, since they never would have had a huge supply of meat at any time during the year, in contrast to the summertime carnivores that we become. Hunter-gatherer and pastoralist life could have created these tastes since it's easier to hunt down animals in warm weather, and since it's less risky to ritually slaughter one of your livestock for a feast during warm weather when the rest of the herd is feeding well and breeding.

As cold weather sets in, it's like we're trying to fatten ourselves up by gorging on easily digestible carbs, just in case it's a harsh winter. It could be to maintain a reserve of energy that could be burned if we encounter little food, as well as to provide us with insulation against the cold.

By the way, "diet" and "dieting" peak in Google Trends right after we've had Thanksgiving and Christmas carb binges. It is not "caused by" the tradition of New Year's resolutions, which is the effect and not the cause -- we picked that time to make ritual resolutions because that's when we naturally think to ourselves, "Good god, what have I been doing to my body lately?" That's surely one reason why dieting doesn't work -- people try it mostly when they're in carb-munching mode and their insulin is too jacked up to let the fat out of their adipose tissue.

There is no peak for diet or dieting before summer, when supposedly everyone is worried about how they'll look with their shirt off or in a swimsuit. And there's no peak after summer, when people might worry about all the burgers and dogs they ate. Deep down we know that loading up on animals is not unhealthy, and we feel no need to diet then, and so we would never make our resolutions during the summertime. The regeneration of springtime and the new pulse of life of summertime would surely make a good background story for why we're making our resolutions to turn over a new leaf, but we just don't have the need to during these times.

I'm not sure whether the wintertime sugar bomb stems more from our hunter-gatherer or pastoralist past, but my hunch is the latter. It was just not possible for hunter-gatherers to find lots of sugar at any time during the year, whereas pastoralists have always existed alongside settled farmers who had domesticated fruits to taste super-sweet (try a crabapple to see how wild fruit tastes), and they also grew really starchy grains and even sweeteners, though they were still fairly rare. The pastoralists could either have just raided the farmers and stolen these ingredients for sweets, or they could have been part of a trading network where they gave up some of their cheese or butter or animal hairs to the farmers. Either way, this would have to wait until after the autumn harvest, or the farmers would have little to offer the herders.

If the farmers had built even more advanced societies, there might even be specialists who had made cakes, pies, etc., already and that these were traded in exchange for the herders' animal products.

Having told that story, though, it seems like the source of our seasonal fluctuation in preference for sugar vs. meat comes from the historical intertwining of both farmers and herders. Without the products of both groups, there could have been no icing, toffee, ice cream, whipped cream, cheesecake, eggnog, cheese danishes, or a plate of cookies or brownies with milk.


  1. Hmmm...I gain a good 5-7 pounds every winter and then lose it every summer.

    My appetite also increases when it gets cold.

  2. You seem to be ignoring the storage issue. What stores well through the winter? Grains, things with enough sugar to resist spoilage, and starchy vegetables. Processed meat also stores well, ham for example, but due to the processing you aren't going to eat as much of it at a time. Plus you have to worry about how long the winter is going to be so you wouldn't want to eat it all up too soon.

    I'd also toss in some metabolism based reasoning. In the winter your body wants a constant stream of things it can easily turn into heat. Protein that takes more effort to break down and makes your body feel full isn't much good at keeping the inner furnace running hot.

  3. The main reason for craving carbs in the winter is the body needs calories to burn and make fat to combat the cold temperature/weather. Which is why most girls in the East Coast have a little more fat than girls in the West Coast.

    Craving of meat? That's probably just a social effect of having more BBQs.

  4. Your reference to the Fourth of July contains the key to understanding the issue. Summer is associated with cookouts, and there is no traditional form of meal more meat-intense than the cookout.

    Being originally from Connecticut I would add that Election Day is associated with cake, namely Election Cake (a form of fruitcake made on, and only on, Election Day), but that would be too obscure for people in the other 49 states.


  5. Here's the thing. If we think that much of human nutrition (and problems it faces in the modern age) is determined by the paleolithic past - and therefore that a paleolithic diet makes sense for our health - then why would we have any cold response? It's highly unlikely any of us have been at cold-winter latitudes for even 40,000 years, a substantial fraction of it post-agriculture, and the paleolithic stretches back hundreds of thousands of years below that. If you think of the paleolithic as taking place mostly in savannah, then you'd have a slightly hotter "winter" dry season and a slightly more moderate
    summer wet season.

    While the paleolithic story is an interesting one, there is better empirical proof to be had in epidemiology and exercise science.
    I've actually made this same observation (about carb cravings in winter) but evolutionary just-so narratives are too easy to spin up to confirm whatever biases we might already have.

    Some questions to test: if you're black, and you live in a cold-winter climate and still get these cravings, we can't explain that evolutionarily. If you live in a non-cold-winter climate and get these, it's also hard to explain (I believe I get it, and I live in frickin San Diego.) Can we explain weight change by activity level? People in Alberta probably aren't jogging and hiking as much this time of year either.

    In general, another problem with the paleolithic diet theory (while I'm picking on it): why is the hominid paleolithic this golden age of metabolic predestination? Can't we have made an impact on ourselves since agriculture? For example, humans from different parts of the world do in fact store fat very differently (stereaptygia in Khoi-San women, cellulite in Europeans, visceral fat in Asians). And most importantly, what about the 40 million years prior to the divergence of hominids when we were nearly obligate herbivores, wouldn't we expect that to still have a huge imprint?

    Obesity is a HUGE reason for loss of health, wealth and happiness and it's getting worse, so I wish we were doing better research and getting clearer answers to these things.


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