Want to Stop Overeating? Play With Your Food!
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Why is it that when you are the person who prepares the Thanksgiving feast, it doesn't taste nearly as good as when someone else prepares exactly the same thing? Whenever I spend all day preparing food, I am just not very hungry when dinner comes, even if I have eaten nothing all day.
Then there are those times I find myself heading into the kitchen with a strong drive for...well...nothing in particular. And I'm not even hungry. I just want to prepare some food. That's all. I want to mess with food. And that can lead to an extra unneeded meal.
We humans do more and more complex food manipulation and preparation than any other creature. I speculate that the drive to play with our food -- to handle, shell, peel, pound, grind, cut, cook, and carry food -- is now built into our genes. A couple of decades ago, it would have been thought that there has not been enough time since we began complex manipulation of food for evolution to act on our behavior. Now, however, we realize that the apparently relatively slow rates of evolution displayed in the fossil record actually often represent long periods in which nothing much was happening interspersed with periods of rapid evolutionary change. In fact, serious evolutionary change can occur in just a single generation or two, as is graphically demonstrated in Jonathan Weiner's The Beak of the Finch: A Story of Evolution in Our Time. In addition, from archeological evidence we now realize that we have been seriously playing with our food for lots longer than we initially imagined.
We have have been leaving our cutting-tool marks on the bones of other animals for about 2.5 million years or more. We have controlled fire for more than 300,000 years. We've had ovens for at least 250,000 years. And for more than 12,000 years we have been breeding and using agricultural crops, many of which are inedible without cooking. (See the discussion by Richard W. Wrangham on the impact of cooking on human evolution in "Out of the Pan, Into the Fire: How Our Ancestors' Evolution Depended on What They Ate," in Tree of Origin (edited by Frans B. M. de Waal)). We have obviously had plenty of time to evolve a drive to play with our food. Maybe when, as kids, we take a piece of bread (food preplayed with by someone else) and we press and roll and play with that bread ourselves until it is a tiny marble-shaped ball, we are following our deepest and most honorable of instincts. Maybe playing with our food is what made us human.
We have sophisticated biochemical and hormonal "satiety" mechanisms that help us determine how much and what to eat. But are they the whole story? Based upon my own reactions, I think some of our satiety mechanisms are more simple-minded. I seem to want variety, for example. A one-pot meal is not as satisfying to me as the same amount of calories spread over several courses. This is true even when the "courses" are big chunks of meat and vegetables dipped out of that same stew.
For me, jaw exercise also matters. A crunchy carrot or two with a meal seems to contribute to my satisfaction all out of proportion to the calories or stomach space involved. A chunk of chuck roast cut and cooked steak style is tough and takes serious chewing work. But it is much more satisfying to me than a much larger piece of tender sirloin. I'll overeat the sirloin. But I can be satisfied by a much more modest piece of the chuck. If my meals for any given day have included nothing crunchy, by evening I find myself craving crackers or potato chips. My "crunch drive" seems to think in terms of potato chips or crackers. But it is satisfied just as well by an apple or some carrots.