A New Wrinkle on Overeating

I just read The End of Cravings by Mark Schatzker which has an interesting new theory (and data to back it up) about what causes overeating.

As you know, I’m an advocate of eating whole foods and avoiding overly-processed foods, and have presented evidence such as in Dr. Michael Greger’s book How Not to Diet, and the Pleasure Trap, by Drs. Doug Lisle and Alan Goldhamer. I also talked about the book Salt, Sugar, Fat, by Michael Moss, that describes how food industry science search for the “bliss point”, the combination of ingredients that make food irresistible. A common theory is that these processed foods are overly tasty, or hyperpalatable, and fool our brains into craving to eat too much of them.

But Mark Schatzker shows some fascinating pieces that don’t quite fit that theory, plus some new evidence. This doesn’t change the bottom line that it’s good to eat mostly whole foods and avoid overly processed foods, but it adds some nuances to the reason why.

First is the case of food in Northern Italy, a region that is widely regarded as having some of the most delicious food in the world. The traditional cuisine contains lots of carbs, fat, meat, and sugar. Little modern overly processed food is eaten there, mostly the traditional fare. And the food is not minimally processed, they include plenty of items like pasta made with white flour. But there is a very low incidence of obesity in this population, and the rate of obesity has not changed significantly in the past several decades, a period during which it has skyrocketed in the rest of the modern world. So what is different about this highly palatable cuisine?

The new theory is that our modern processed food has many altered ingredients that fool the brain. Artificial sweeteners, and a slew of ingredients that replace fat (or the “mouth feel” of fat) top the list. Our brains have exquisitely tuned mechanisms that predict the nutritional content of food. It’s been known for a while that artificial sweeteners don’t work, with the fascinating phenomenon that people who use them tend to eat more of other things to replace the missing calories. So you drink a diet soda, and the brain says “ok, that’s 150 calories I just took in”. But then it digests the soda and there were no calories. It will make you crave 150 calories of something else to replace the calories it got “swindled” out of.

There is fascinating research described in the book that illustrates this mechanism. Other artificial ingredients like the “fat replacers” have similar effects. We end up eating more calories because our brains are not satisfied.

Another interesting contributor to this effect is that our brains have separate mechanisms for “craving” and “liking”. We “crave” something when we are anticipating the pleasure of it, and “like” it when we actually experience it. This is becoming known as a mechanism contributing to addiction. The first hit of a substance like heroin can lead to a tremendous high, which jolts the “like” mechanism. Then someone can subsequently crave it. But future hits deliver a weaker and weaker stimulation of “like”, but craving remains strong because of the memory of the earlier high. A similar things happen will all kinds of things we crave: they overpromise pleasure and underdeliver on it. This was recognized as a major contributor to the “unsatisfactoriness” of life in Buddhist philosophy 2500 years ago, and is now borne out by science.

A good example is potato chips. I don’t think many people would name them as the top of their list of palatable foods. Yes, they taste good, but better than ice cream or good quality chocolates? Yet it is potato chips that famously had commercials with the tag line “bet you can’t eat just one”. They are hypercravable, not hyperpalatable. This works with a food addiction mechanism similar to the heroin description above. I remember it happening with me with a brand of low-fat dessert called “skinny cow”. These were ice cream sandwiches that had about 100 calories, probably less than half of a similar dessert made with real ice cream. They had a long list of ingredients, many I’m sure to mimic the taste of fat and improve “mouth feel”. And they tasted great. But somehow they were not quite satisfying. So I’d eat another. I’d end up chasing whatever brain was missing until I ate the whole package of six. This was about three times the amount of calories as if I’d just eaten one ice cream sandwich from real ice cream.

In contrast to our modern overprocessed food, highly palatable traditional food like that from Northern Italy has no artificial ingredients. If it tells your brain it’s sweet, it delivers with sugar. If it tells your brain it’s rich with fatness, it delivers with fat. So people eating this type of food tend not to overeat because the brain and it nutrition-sensing mechanisms are satisfied with an appropriate amount of calories.

This is not to say that the cuisine of Northern Italy is the ideal we should aim for in all respects. There is no mention of the health status of the residence of this region in the book, nor is it known for particular longevity. I think the lesson is to stick with whole foods as much as possible, but for health and longevity, perhaps mimic the cuisine of the Blue Zone populations.

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