Tuesday, July 23

Whole30 Part IV: Brain Signaling, Satiety and Satiation

Just over a week to go until the August 1st Whole30.  It’s my hope that by the end of this post you will have a solid foundation to understand why the Whole30 includes some foods, and excludes others.  The principles that I outline below will round-out the framework so that we can launch into the technicalities of:  eat this, not that.

As a quick re-cap, in the first two posts (Part I, Part II) we discussed how Jessie and I first came across the Whole30, and the benefits, purpose and intent of the program. Then, we dug into some high-level science.  We uncovered why calories don’t really matter, and that weight regulation all comes down to a hormone called insulin (Part III).

Onward and upward…

Primal Food Instincts

I think it’s incredibly important to understand humans’ primal instincts with regards to nutrition. It might sound silly, but it was without a doubt another pivotal “ah-ha!” moment for me when I first started my research.

The book It Starts With Food has a terrific section entitled “Ancient Signals in a Modern World.”  In it, the authors point out that humans have evolved to be hard-wired to appreciate certain tastes. Specifically, our reward-circuits light up in our brain for foods that are sweet, salty and fatty.  Our brains biologically associate foods that are sweet with safe sources of energy.  Foods that are salty indicate a means to conserve fluids.  And foods that are fatty represent a dense source of calories.

In the past, these signals were critical for our survival in nature.  The problem now, of course, is that these signals still exist, but the foods are processed garbage.  You see, these signals “weren’t designed to tell us which foods were delicious – they were designed to tell us which foods were nutritious.”  M&M’s and French fries light up the pleasure center in our brains just like they’re supposed to, the issue is that they’re lacking in quality nutrition. Hence, “ancient signals in a modern world.”

This is a big problem for us, and a big money-maker for junk-food manufacturers. 

Satiety and Satiation

This concept of food stimuli and reward circuitry leads us to another important principle: satiety (suh-tie-uh-tee) and satiation (say-shee-ay-shun).

Satiety is the point at which your body realizes it requires no additional nutrition.  It is regulated by hormones via the hypothalamus.  Let’s say you’re eating Jessie’s awesome kale salad.  As the kale moves through the digestive tract the body takes inventory of what it’s receiving.  The point at which the body realizes it has enough energy and nutrition (vitamins + minerals) it will signal to the brain to stop eating.  Often times it can take several hours for the brain to realize the body is well-nourished, so we can’t rely on satiety alone to know when to stop eating. Thankfully we’ve got satiation as a fail-safe.

Satiation is based in the brain.  It’s essentially your brain estimating how much you’ve eaten based on quantity, taste, smell and texture. It’s why we have diminishing returns with many nutritious foods we eat; each bite is less appealing than the bite before.  At some point the brain estimates that you’re topped off and suggests that you stop.

Satiation is “I don’t want any more.”  Satiety is “I don’t need anymore.”

But what happens if the food is lacking in adequate nutrition?  What if the food doesn’t have quality fats, vitamins, minerals, protein, etc.? Furthermore, what if the food lights up the reward signals in the brain?

With M&M's as our example, one takes a hand-full of M&M's down, the refined sugar lights up the reward signal in the brain, and the brain says "keep it coming!" Satiation doesn't kick in because there is no diminishing returns with eating processed junk food. You see, processed junk food is over-stimulating; it's infused with sugar, salt, fat and chemicals that would never be found in nature. The second bite tastes as good as the first, the tenth as good as the ninth. Satiety also doesn't kick in because the body can't be fooled: there's no quality nutrition in M&M's. 

The end result is that you'll eat until you're physically full, a feeling I'm sure we all know too well. Sometimes people will eat these foods (which the book refers to as "foods with no brakes") until they are literally ill.  I know Louis C.K. has (apologies for the language).

I hope this post was useful in putting some things into perspective with regards to eating. Next installment we'll hammer through some tips and lessons learned from our previous Whole30 as we launch into August ready to rock and roll.

Click here for Whole30 Part V.


  1. These are all SO helpful! Makes me so excited to start the Whole30 for the first time knowing y'all will be there to support all the way through.

  2. I'm so happy you're enjoying them. One or two more posts to bring it home, and then we'll tackle this thing head-on!


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