The Gila Monster's Guide to GLP-1

I’m 58. 

I haven’t really been to a doctor since I was 18. 

Recently, I hired a concierge doctor to run blood work. Everything was fine, but there was a small indication I might have pre-diabetes. 

So he put me on something called tirzepatide. 

It's a once-weekly shot that mimics two gut hormones—GLP-1 and GIP—the ones in charge of blood sugar and appetite. 

Everyone's on it. Now I'm everyone.

Then one day I doubled the dose, felt awful, and thought: this must be the peptides kicking in. This is terrible! 

I was wrong. I had COVID.

So, to figure out what to expect, I called Charles Duhigg. 

He wrote The Power of Habit. 

He's also lost 45 pounds on this stuff over two years. He explained what I'd actually signed up for.

Here's what I learned.

Gila Monster Venom

Peptides are all the rage right now. 

They're just short chains of amino acids, the same building blocks that make up proteins, only smaller. 

Your body already runs on them; they act as signals telling cells what to do. Tirzepatide is one of these. 

The longevity crowd uses "peptides" as a catch-all for a whole menagerie of these compounds, from the GLP-1 shots everyone's on to more exotic stuff people inject hoping to heal faster, sleep better, or outrun time. 

And the weirdest part: 

This whole class of GLP-1 drugs came from Gila monster venom. 

The lizard can shut its metabolism down for months. A researcher wanted to know why. That discovery became the drug exenatide (Byetta), the first GLP-1 medication, approved in 2005. 

Every GLP-1 drug since, including tirzepatide, builds on that lineage. 

Now, here’s what they do. 

Food Noise is Real 

Charles described sitting at a table with a basket of fries. Not hungry. Full, even. And still his hand reaches over. He eats them, barely aware he's doing it.

That reach is a habit. 

Every habit has three parts—a cue, a routine, a reward. The fries are the cue. They trigger a craving for salt and crunch. The craving pulls your hand. 

You obey.

What the GLP-1 does is quiet the cue. You see the fries and nothing fires. The noise in your head goes silent.

And into that silence, Charles said, something extraordinary becomes possible. A window opens. 

For a while—months—your habits go soft. Malleable. You can rewrite them. 

And if you rewrite them well, the new habits stay even after you stop the drug. If you don't, the weight comes roaring back the moment you quit. Most people quit within two years.

The drug isn't the miracle. The window is.

You Have Two Brains 

Some habits drag other habits behind them. Charles calls these keystone habits. 

Eat a little less and it's easier to run. Run and it's easier to eat the salad. Drink less and you sleep better. Sleep better and you focus at work. Focus at work and—

You see where this goes. One small change tugs a whole chain.

And the key part: Your brain isn't listening to what you say. It's watching what you do.

You have two brains. 

The front one sets goals: I want to lose 20 pounds. I want to run a marathon. That's your stated preference.

The deeper one—the basal ganglia—ignores every word of it. It watches your behavior. 

You didn't run this morning. You ordered the hamburger. So it concludes: this person doesn't actually want those things. And it quietly builds you into the person you keep acting like, not the one you keep announcing.

But flip it. Skip the fries a few times. Take the shot every week. The deep brain notices. Oh. He's someone who takes care of himself. And slowly the identity shifts to match the behavior.

I told Charles this sounded like the placebo effect. Like Todd Herman's alter ego stuff—Kobe becoming the Black Mamba before a game. 

Charles said that's exactly it. You program the deep brain by acting like the person first.

The placebo doesn't change your biology. It changes who you think you are.

Hear About My Journey

I'm now three weeks into my GLP-1 journey. 

I'm keeping a journal. Because Charles warned me about the one thing that ruins all of this—you don't notice yourself changing unless you force yourself to watch.

If you want to learn more about these crazy drugs—and what Charles told me to expect—listen to the entire podcast.

Click here for the whole thing.