I’m currently sat in quite a swish pub in a small village outside Cambridge. It is a Thursday evening in early December, so it’s dark and freezing outside. Here, however, there is a warm cozy fire, the whole place is decked out in festive decorations. Michael Bublé is crooning Christmas songs on the radio, and I have a large glass of Malbec in my hand. Life is good.
It’s been a long day (long week actually), so let me attest that this is definitely the place to be. This is one of those ‘gastropub’ establishments that serves lovely food, and I’ve just enjoyed a weekday date night with my wife Jane.
For dinner, we both had the cured trout to start, then for our main courses, Jane had the hake, and I had a burger and chips. The portion sizes were healthy, and both of us were pretty full by the time we were finished.
Then you know what happened next. The waiter comes along with the dessert menu asking "Could you be tempted?" Yes, we most certainly could. And full though we were, and on a weeknight as well, both of us ordered dessert. I had a sticky toffee pudding with ice cream, and my wife had a slice of tarte au citron with crème fraîche. Like clockwork, the dessert stomach strikes once again.
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Here is the question though, why is it specific to desserts? Would I have had another burger? Would Jane have had more hake? Absolutely not. So, what is special about desserts?
To answer this question, we have to look to evolution. Flashback to 50,000 years ago on the Serengeti, and your ancestors are dragging an antelope back to the village. Let us just say it has cost them, metabolically speaking, 2,000 calories to stalk, chase and bring down.
When they get back to the village, they would clearly have to consume at least 2,000 calories to recoup their expenditure, otherwise it wouldn’t be sustainable. But there is no guarantee that they will successfully get an antelope the next time out. This means if they only ate to their metabolic need, they wouldn’t survive very long.
That is when the hedonic part of the brain kicks in. This governs the feeling of reward we all get from eating, driving us to chow down more than we actually need. But how do we get past the mechanical difficulty of a stomach packed full of 2,000 calories of food?
Well, our brains become pickier. They begin to crave foods that are more calorically dense – foods which for every given gram contain more calories. This allows us to fill in all the nooks and crannies in our stomachs.
So, what foods are the most calorically dense? Those that are high in free sugar and fat. And what foods are high in sugar and fat? Desserts.
In other words, your dessert stomach is actually an evolutionary holdover from your days in the Serengeti. It's there to make sure that even when full, you are still craving the right types of foods to ensure you are able to maximise your caloric intake at every meal. There was never, after all, a guarantee of when the next meal would arrive.
You've probably spotted the obvious issue here: while this drive kept us alive in regular cycles of feasting and famine, many people today live in a cycle of feasting and, well, more feasting. I most certainly did not need that sticky toffee pudding (although I really enjoyed it, and did not regret it for one minute!).
Incidentally, the ‘dessert stomach’ isn’t just some weird human phenomenon. Now, I completely understand that a lion is not going to be topping off their freshly killed antelope luncheon with a crème brûlée and a glass of chilled muscat. But let’s just consider the grizzly bear during the salmon runs in the Pacific Northwest of America as an example.
Grizzlies arrive at the swimming buffet of the salmon runs, which take place in the autumn, with the intention of storing as much fat as possible for the coming winter hibernation.
When they first start, the bears eat pretty much the whole fish, down to the bone. However, as they get more and more full, and store more and more fat, they switch to just eating the skin of the salmon and the thin layer of fat that lies underneath. Why? Because this is the most calorically dense part of the fish. They begin to change what they are eating to maximise their energy storage.
So, while desserts are clearly a human cultural construct, the phenomenon of maximising the calorie density of food that is craved as one gets full, is conserved through evolution. So, yes, it's not your fault you can find room for dessert, even after a satisfying meal.
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