Hunger and Eating

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There is hunger and then there is eating.

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Well, at first glance, eating seems pretty simple—that somebody's hungry. Their body sends out a signal, they eat. But of course, it's much more complicated than that.

There is a pretty complicated relationship between hunger and eating. And I think that one of the big factors is the environment that you live in.

Hunger is a biological motive. Eating is a complex interaction of biological, cultural, social, and psychological factors that determine when, how much, and how often you respond to your hunger. In order to understand the regulation of hunger and eating behavior, we need to begin with some basics on how food is converted into energy in the body. The food that you eat is broken down by enzymes and absorbed in your intestines.

The simple sugar glucose is the main source of the body's energy. Increases in the hormone insulin, secreted by the pancreas, diminish blood glucose, partly by converting it to stored fat. If your blood glucose level drops, you won't consciously feel this change.

Signals go out to the body—to the brain, but other parts of the body, as well—that it's time to start eating, stop eating—whatever it happens to be. And these are very powerful. It used to be that the body's ability to regulate itself via those ancestral physiological mechanisms were very well-suited to the environment, because there wasn't a lot of junk food in the environment that fooled the body. Now, it's a whole different picture.

The body's weight, pretty simply, is determined by calories in, and calories out. How much you eat is essentially the calories in, and how many calories you burn—not only through exercise, but your basic bodily processes that have to have energy to be sustained—your heart beats, your blood is moving through the body—all these things require energy. But it's the balance of calories in, calories that determine body weight.

If your caloric intake exceeds the amount of calories expended for energy, you experience positive energy balance. There is more glucose than your body needs for its energy requirements. And the excess glucose is converted into reserve energy or fat.

Conversely, if you diet or fast, negative energy balance occurs. Caloric intake falls short of the calories expended for energy. If this imbalance continues, body fat stores shrink as the reserve energy is used for physical activity and metabolic functions. Insights gained from neuroscience have informed our understanding of the role of the human brain in hunger and eating.

One of the areas of research that goes back the furthest is interest in the hypothalamus. And so scientists—many, many years ago—discovered that looking at different parts of the hypothalamus could start to explain what was happening in the body weight, and the hypothalamus could both start eating—other parts of it could stop eating.

The hypothalamus is a subcortical structure that monitors and responds to some of the key appetite hormones in the body.

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When we're hungry, when we're eating, and when we are full, the hypothalamus is constantly monitoring key hormones and responding accordingly. One of these is ghrelin—a hunger-arousing hormone secreted by an empty stomach. One of ghrelin's counters is cholecystokinin—abbreviated CCK—released by a full stomach, which helps to slow down our eating behavior. This complex interaction of appetite hormones and brain activity may help explain the body's apparent predisposition to maintain itself at a particular weight level.

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So there are plenty of environmental cues that trigger people to eat. It so happens there are many more now than used to be the case. But even in the old days, there would be things like, you heard the bell rang and it was time for dinner.

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Or it became lunch time and you'd see a clock on the wall and you'd look at it, and you'd say, oh, I think it's time to eat now. And then all of a sudden, you'd start to feel hungry.

There are those kind of cues, or you'd smell something being cooked in the kitchen. Those are in the normal range of cues. And they probably serve a useful purpose and don't lead people to overeat. The problem now is that the cues are everywhere all the time, so that the food environment has become very toxic, because of the availability and access that people have—but much more to the unhealthy choices than healthy ones.

Unfortunately, the environment that we live in right now, there are a lot of things that are high in sugar, salt, and fat. And those are heavily marketed to kids. They are heavily palatable.

You can't drive anywhere without going past food cues. You see the signs of the fast food restaurants. Everyone has a drive-in window to make it very easy. If you're a kid in school and you walk past those soft drink machines everyday, those are cues. And not only do people see more opportunities to eat, but they're seeing bigger portions of what it is to eat, and that becomes another environmental cue that triggers overeating.

I think that childhood obesity has become such a big problem that researchers, politicians, health professionals are all really looking for some solutions.

So what would you change? Smaller portion sizes? You can mandate that. The government has the authority to do that.

You could certainly restrict the marketing of bad foods that goes on to children. You can certainly get rid of junk foods in schools. A lot of places around the country are doing that already.

You can change the relative price of foods with tax strategies. So you can charge more for less healthy foods and less for more healthy foods. There are a lot of things that can be done that we're now really beginning to think about seriously, as a country. And I'm all for it.

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