Harvard Health Letter

Controlling what - and how much - we eat

Here is the problem: we Homo sapiens evolved to cope with conditions that predominated during the Paleolithic period, when humans hunted and gathered, and fat, salt, and sugar were in short supply. To ensure that we ate adequate supplies of each, we evolved a craving for them. In fact, some of the brain mechanisms involved in our pleasurable response to sugar and fat are the same as those involved in our response to opioid drugs like morphine and codeine.

But now we live in an environment that is brimming with food and drinks that satisfy these cravings — and, in the process, make us overweight, cause illness, and shorten our lives. An adult can get by on as little as 500 milligrams (mg) of sodium a day; the average American intake is about seven times that amount, or 3,400 mg. Humans can certainly live without sugar (and, in fact, without any kind of carbohydrate as long as some fat and protein are available), but Americans now consume, on average, about 20 teaspoons of added sugar daily — and that's above and beyond the sugars found naturally in fruit, vegetables, and dairy products.

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