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Hungry or Not: What Three Levers Control Your Appetite?

Researchers have identified three distinct neural pathways that control our desire to eat. Two rely on our desire to avoid discomfort. The third is all about pleasure. Understanding these three neurological triggers may help tame an out of control appetite.

By
Monica Reinagel, MS, LD/N, CNS
4-minute read
Episode #522
Hungry man reaching for brownie.

If you’re trying to manage your weight, chances are that you have spent a fair amount of time thinking about hunger. How can you eat less without feeling hungry? Is there any way to control your appetite? How do people who weigh less do it? Do they simply not experience hunger? Are they hungry all the time? How can you distinguish between true hunger and the urge to eat?

As someone who coaches people on sustainable weight loss, these are questions I’ve spent a lot of time thinking (and writing) about, as well. Today I want to tell you about the three different ways our bodies register or experience hunger. 

In my recent episode on how calories in food are determined, I talked about the hazards of relying too heavily on calorie counters and calculators. I pointed out that we probably can’t rely entirely on our hunger or satiety signals to tell us if we need food and when we’ve had enough.

And I bet that might might have been what triggered a listener to phone in and ask what I thought of intuitive eating and whether there was any good research to support it.

Does intuitive eating work?

Intuitive eating is a popular concept these days and people throw this term around pretty loosely. It’s hard to know sometimes exactly what they mean by it.

For some, it just means not following rigid diet rules. I’m all for that! But if you’re having trouble managing your weight, that approach alone may not be enough to solve the problem. I talked more about the strengths and weaknesses of intuitive eating as an approach to weight management in episode #397.

On a closely related topic, Cheryl from Massachussetts emailed to ask:

Even when I eat a good sized meal with adequate levels of protein, fat, and fiber, I can feel hunger after just an hour or two. And sometimes when I'm experiencing digestive upset, it feels like hunger. Do other people have a hard time distinguishing between digestive activity and hunger pains?

You bet they do, Cheryl! In addition to all the environmental, emotional, and social cues that can fake us out, there are a number of digestive disorders, everything from acid indigestion to IBS, that can cause false hunger or, conversely, mask hunger symptoms.

I have more tips on how to tell if you’re really hungry in episode #387.

Which brings me to some fascinating research that my sister (who is a neurobiologist) recently forwarded to me.

The three pillars of appetite—what prompts us to eat?

Researchers Scott Sternson and Anne-Kathrin Eiselt of the Howard Hughes Medical Institute in Chevy Chase, Maryland, recently published a paper in the Annual Review of Physiology titled "Three Pillars for the Neural Control of Appetite." Sternson and Eiselt describe three neurological mechanisms that control appetite. 

Low blood sugar

The first is triggered by low blood sugar. When our blood sugar levels get low, we start to experience unpleasant sensations which increase in intensity until we get something to eat. (Interestingly, these unpleasant sensations to start to diminish as soon as we have access to food...even before we’ve consumed it.)

A stretched stomach

The second neural pathway is triggered by the proprioceptors in our stomachs that tell us that our stomach is full. As our stomach stretches, we feel less comfortable, which decreases our desire to eat.

Our senses

The third appetite control mechanism is triggered by our senses. The sight, smell, and taste of palatable foods arouses pleasurable sensations that entice us to eat.

We’ve talked about all of these concepts here on the Nutrition Diva podcast before. But Sternson and Eiselt have shown that these three mechanisms are governed by completely different neural pathways. They are, to some extent, redundant systems. Here’s anther thing I found really interesting about their work...

Avoiding pain versus seeking pleasure

The first two levers of appetite (low blood sugar which increases the urge to eat, and a stretched stomach, which decreases the desire to eat) are what Sternson and Eiselt refer to as aversive signals. In both cases, our behavior (to eat or to stop eating) is triggered by the desire to relieve an unpleasant sensation. 

But the third lever, the presence of appealing food, is exactly the opposite. In this case, our response is governed by the desire to experience more of a pleasurable stimulus.

The first two levers of appetite seem purely functional. When an animal needs food, the pain of hunger drives it to seek nourishment. The discomfort of an overly full stomach prevents the animal from over feeding to the point of physical harm.

But the third lever, the presence of appealing food, is exactly the opposite. In this case, our response is governed by the desire to experience more of a pleasurable stimulus.

The third lever, however, is more hedonistic. In this case, the drive to eat is governed not by the physical need for food but by the availability of pleasure-producing foods. What’s the function of that?

Perhaps in a time of food scarcity, this may have served to motivate animals to take advantage of occasional nutrient or energy windfalls. But in an era where we are surrounded by an excessive amount of calories, many of which have been literally engineered to trigger our pleasure centers, our innate drive to consume tasty food is literally killing many of us.

But this insight can also help us take control. Knowing that the presence of palatable food is likely to provoke a strong drive to eat or keep eatingcompletely apart from our biological need for foodunderlines just how important it is to control our food environment, rather than rely on our willpower. And I have three practical tips for the willpower-challenged in episode #266. 

If you’ve got a question or comment for me, you can call the Nutrition Diva listener line at 443-961-6206. I’d love to hear from you.

About the Author

Monica Reinagel, MS, LD/N, CNS

Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes' most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation's leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show. 

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