How Hunger Works

Understanding the hormones—leptin and ghrelin—that turn your hunger switch on and off.

How Hunger Works

There’s evidence that two hormones have much influence on our hunger and satiety levels. Let’s look into the science behind them.

Lovin’ Leptin: The Satisfaction Hormone
Fat produces a chemical signal in your blood to stop eating. It’s self-regulating. The problem happens when we override our internal monitor system and continue eating after we’re full.

Fat curbs appetite through the important chemical in weight-reduction: leptin—a protein secreted by stored fat.

The stimulation of leptin shuts off your chemicals and triggers you to burn calories, by stimulating CART.

Unfortunately, leptin doesn’t always work the way it’s supposed to.

MORE: Outsmart Your Eating Instincts

How Hunger Works

When given to rats, it decreased appetites, as it should. When given to humans, it made them thin... then something strange happened: They overcame the surge of leptin and stopped losing weight. A surge from the pleasure center in your brain can overrule leptin’s full message.

This doesn’t mean that leptin will always lose the chemical battle. The challenge is to make leptin do its job so the brain demands less food.

If you walk 30 minutes a day and build some muscle, your cells will become more sensitive and responsive to leptin.

QUIZ: Are You Getting Enough Exercise?


MORE: Exercise & Your Appetite: The Truth

Ghrelin Is the Gremlin: The Hunger Hormone
When you’re stomach’s empty, it releases a feisty chemical called ghrelin. This stimulates NPY. If you diet by deprivation, ghrelin secretion will increase and send more signals to eat! This obviously helps override your willpower, causing chemical reactions that give you little choice but to submit to cookies.

Ghrelin also increases the release of the growth hormone (building you up and out). Your stomach secretes ghrelin in pulses about every half hour. This sends subtle impulses to your brain. When you’re really hungry (or dieting), the messages come every 20 minutes or so. And, they’re amplified. After long, your body can’t ignore the messages. It’s nearly impossible to fight the biology of your body.

The vicious chemical cycle stops when you eat. Your stomach needs to be full to reduce your ghrelin levels and appetite. If you could keep those ghrelin gremlins from making so much noise, you’ve got a chance.

Use Food to Work With Your Hunger Systems
Good news! You can control the satiety center with your food choices. Food is a drug, making different chemical reactions take place and sending messages throughout your body.

You set the tone for these orders through food. Eat the right foods (nuts) and your hormones keep you feeling satisfied. Choose the wrong foods (simple sugars) and your body goes haywire hormonally. You can become addicted to harmful foods.

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