Philip J. Goscienski, M.D.
May 2011
Ghrelin is a hormone-like chemical produced in the empty stomach that increases the appetite. Theoretically, when the stomach is full it turns off the production of ghrelin and thus, the urge to eat more. In addition to ghrelin, cholecystokinin is a hormone that acts to suppress the appetite. It sends a signal to a region of the brain known as the appestat, and the desire to eat diminishes. If it were only so simple! There are dozens of factors that come into play and the appestat is more a concept than an actual structure.
Hunger isn't the only factor that increases our appetite for food. Stress will override our built-in biological control mechanisms and certain foods fail to trigger the feeling of fullness. The appestat simply doesn't work in some obese persons.
If a full stomach sets the appestat in motion, it figures that loading up on foods that have lots of bulk but few calories will help to control weight. That's precisely what keeps present-day hunter-gatherers lean and it's likely that it worked in the Stone Age, too. Until the development of refined grains and sugars, about half the calories in the human diet came from whole grains and vegetables. Both are rich in fiber but relatively low in calories. Anthropologists estimate that Stone Agers ate 3 to 5 pounds of plant foods every day. There were no high-calorie foods back then. Their meat had little fat, grains had almost no place in their menu and plain sugar didn't exist. We can follow their example most of the time and still leave room for whole-grain foods and occasional sweet treats.
About a quarter of the calories that Americans consume come in the form of soft drinks, a double whammy. Besides the high calories (a 12-ounce soda contains the equivalent of about 8 teaspoons of sugar) liquid foods don't trigger the appetite control mechanism. Fructose, which is found in most soft drinks and in table sugar, also fails to register with the appestat. It's probably not a coincidence that the obesity epidemic started at about the time that the food industry discovered high fructose corn syrup.
Sometimes the sensation of hunger is really thirst. A tall glass of water can usually alleviate the feeling of hunger, with no calorie penalty.
It takes about 20 minutes for the appestat to kick in, so eat slowly, just like Mom told you.
Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at drphil@stoneagedoc.com.