Brain Chemistry and Hunger: What’s Making You Want To Eat?

Gluttony is a plague on Western society.

…But this isn’t exactly news.  We all know the “SAD” diet (Standard American Diet) is a disgraceful binge on saturated fat, trans fat, high-glycemic carbohydrates, refined and de-natured foods.  This is a recipe for fat bodies and poor health.

Oh, yes, and there’s plenty of advice about how to eat less. You’ve heard it before:

Chew your food thoroughly.  Don’t eat in front of the TV.  Avoid high GI foods that trigger cravings.  Chug a glass of water before your meals.  Avoid “grazing.”  Don’t dine out so often.  Give yourself “small allowances,” but stick to your plan!  Give it time, your stomach will “shrink” and you’ll feel more full on less food.

Blah!  Blah!  Blah!

This helps a few, but I’m interested in knowing why, when I try to re-duce my own calorie consumption (even modestly), it feels like some kind of switch has been flipped, and my brain screams, “Eat, dammit!  Eat everything you can find!”

Hunger is an extremely complex subject–too vast to cover in a single article.  But I would like to address the aforementioned “switch.”  The chemistry behind it…

Hunger and Brain Chemistry

Everything boils down to chemistry.  Your emotions, your metabolism, physiology.  Your relationship with food is one of chemistry.

1) Serotonin: The happy neurotransmitter!  It regulates mood, sleep, muscle contraction.  You know what else?  Hunger! It suppresses it.  Most of your serotonin is located in your GI tract, where it regulates intestinal movement.  This chemical is released when you eat carbohydrates.

Your overall diet has the greatest influence of your level of serotonin.  The amino acid tryptophan is the building block of serotonin, but ingested through protein-rich food, tryptophan has a hard time making it past the blood brain barrier, due to competition with other amino acids.  When carboyhdrates are consumed, thereby raising blood sugar and insulin release, those competing amino acids get directed to the muscles, leaving tryptophan free to do its work in promoting serotonin.

2) Dopamine, Norepinephrine: These neurotransmitters influence your level of alertness, which includes your ability to concentrate and your reaction times. Your body produces more dopamine and norepinephrine when you eat protein-rich foods. Proteins are chains of amino acids, and the relevant amino acid here is tyrosine.

That’s nice to know, but what’s it all mean?  Dopamine is an extremely powerful neurotransmitter, associated with all kinds of mood disorders and addictive behaviors.  It’s the “reward” chemical.  Your diet-related addiction to dopamine can have a severe impact on your eating patters–particularly in matters pertaining to hunger vs. satisfaction!

Hunger is physiology; satisfaction is psychology.

We love dopamine.  There’s no way around it.  And we love foods that contribute to our levels of dopamine.  Unfortunately, eating lots of protein-rich foods (filling you up temporarily) actually inhibits your gains in serotonin (the appetite-suppressing chemical). The body has a very difficult time deciding whether to digest carbohydrates or proteins, because these different foodstuffs require different PH balances in the stomach.

Ahh, but combine protein and carbohydrates (ice cream, anyone?) and you have a nuclear weapon against your brain. On the one hand, the serotonin derived from the sugar will give you a life, and on the other hand, the opioid behavior from the dairy protein with sedate you wonderfully.

3) Ghrelin: This is the only known “hunger hormone.”  It is extremely persuasive.  In fact, it is more persuasive that any of your satiety hormones.  Ghrelin is produced when the stomach is empty.  It says, “Fill me!”  Individuals who have had gastric bypass surgery end up with lower levels of ghrelin, because the surgery reduces the amount of ghrelin-producing tissue.

Production of ghrelin is part of your circadian rhythm (your “body clock”) and peaks and dips many times throughout the day.  Because ghrelin is strongly associated with an empty stomach, it gives one a compelling reason to eat smaller amounts, more frequently, ultimately regulating ghrelin’s influential power, not to mention your blood sugar (low blood sugar also triggers ghrelin release).

4) Neuropeptide Y: Watch out for this guy.  NPY’s effect is a desire to increase food intake, and promote the conversion of energy into fat storage. What causes elevated levels of NPY?  Stress, a high-fat and high-sugar diet, and high levels of abdominal fat.

This is huge!  Think about it.  Most people stressed out about losing weight want to stop their high-fat, high-sugar diets!  And yet, as a result of their lifestyle, they have uber-high levels of NPY circulating in their bodies, encouraging them to eat all the time!

5) Galanin: This is a neuropeptide is associated with your intake of fatty foods.  When you eat fat, you produce more galanin, and galanin in turn increases your desire for fatty foods.

Oh, and it gets better.  Alcohol consumption increases galanin, and galanin also increases your desire for alcohol. See “Why Alcohol Makes You Chubby.”

6) Cortisol: This is one of the most widely-reference culprits.  With good reason.  Cortisol is the “stress hormone,” released by the adrenal gland.  Stress is a fact of life, no doubt.  But excessive stress (hence, elevated levels of cortisol) is more powerful than even the best diet and exercise program.

I’m serious.  Even if you’re doing everything by the book, stress alone will make you retain weight.  It makes you hungry.  It inhibits the production of serotonin. It interferes with sleep.  And it promotes the storage of abdominal fat! Happiness and balance in life cannot be stressed enough!

See, “Your Hormones: How They Affect Your Weight (part 2: Cortisol)”

Wow, so in light of all this information, what should we do?  Stay tuned.



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  1. Your Hormones & How They Respond To Exercise « Maria Mae Stevens
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