7 min read

I paid $800 to lose 8 pounds - An Experiment with Continuous Glucose Monitors

Most days you scroll through twitter and get nothing out of it.

Some days you see tweets like this:

Tweet from Justin Mares

Lose weight? Free money? What's the catch?

You have to send this guy $800.

If someone on twitter asks you to venmo them $800, please run away.

I would have run away too, but this proposal was tempting--monetary incentives! weird experiments! group accountability! cool cyborg tech gadget!

I couldn't resist.

Fortunately for me, Justin Mares is a real person and the founder of two food brands: Kettle & Fire and Perfect Keto. If he were to run away with my money I could always send mean tweets to his companies :)

How the Justin Mares Challenge Worked

Here's what happened:

  1. I paid Justin $800.
  2. Justin sent information on how and why to eat a ketogenic diet
  3. Next, the team at Levels Health sent me a continuous glucose monitor
  4. Everyone else crazy enough to do this challenge joined a Whatsapp group
  5. We all installed our glucose monitors on the same day
  6. For the next 28 days the goal was simple: keep your blood glucose levels below 140 mg/dL. Everyday you're successful, Justin pays you $25. If your blood glucose reaches 140 for just a brief moment, no money for you.

What's a Continuous glucose monitor?

A CGM is a device that continuously measures how much glucose (think, sugar) is in your blood at any given point. For instance, right now I have 81 mg/dL of glucose in my bloodstream. These devices are convenient for diabetics. Instead of pricking your finger you can wear this little plastic monitor.

A continuous glucose monitor on my arm

*The white disc on my arm is a continuous glucose monitor*

To get the data from the monitor, scan it with your phone. Using NFC, your phone reads the past 8 hours of glucose levels from the device. Scan a few times a day and you get a full 24 hours of data.

Installation and removal of the device was painless, though it's weird to think about a needle just sticking in your arm for weeks at a time.

Chart of my glucose levels during a typical day of this challenge

The Levels Health app collects data from the CGM. It's got some other neat features like food and exercise tracking. Based on when you eat certain foods and how your insulin levels respond, the app runs some analysis to give 'food scores'.

Quantified Self nerds are either salivating right now or already wearing one of these 😂.

The Challenge

Keto Flu

The hardest part of keto is always the first few days. Nausea, fatigue, and mental fog are all common when starting a ketogenic diet. When you stop eating carbohydrates, your body undergoes a few hormonal changes as it shifts into making ketones. Veterans of low-carbohydrate diets call this transistion period the keto flu.

A big part of reducing these symptoms is making sure to get enough electrolytes. I used nuun tablets because I had them and they taste decent enough. There are cheaper ways to do this, like making bone broth or your own electrolyte mixes.

A New Normal

My new diet? Meat, eggs, avocados, cheese, nuts, and fibrous veggies. There's actually a ton of delicious meals you can make while on keto, once you get over not having a pile of carbohydrates on your plate. If I was crunched for time I found I could get away with a Quest bar.

My energy levels stabilized after a week or so. I didn't have a direct way to test if I was in ketosis, but the difference felt obvious. I no longer craved carbs, and I stopped having afternoon energy dips. My energy levels felt stable all day, though a little lower than baseline.

I lost 5 pounds in the first 10 days. Most of this was water weight, but it's really motivating to see results so early in the process.

For exercise, I continued lifting weights and going on short daily walks. Unfortunately, I never had much energy in the gym. I could get through my workouts but wasn't adding weight to the bar. This kind of thing is typical when losing weight, but it felt more pronounced than cutting on more standard diets.

It was nice to have a group of people going through the same challenge. The Whatsapp group helped with useful tips for recipes, and everyone encouraged each other to do their best.

Messing up

After 20 days I had a perfect record. With only a week left to go I aimed to get all of my money back...

...but I let my guard slip.

To replace our weekly in-person meetups, a group of my friends started scheduling zoom calls. It was almost time for the call but I hadn't had dinner yet. Rushing, I grabbed a premade broccoli-cheddar soup from the fridge and dumped it into a pan. The soup had some carbohydrates, but I had eaten it before and didn't spike my levels, so I figured I should be okay.

During the call, I mindlessly spooned soup to my mouth while chatting with my friends.

Out of habit I scanned my CGM. 130.


One hundred and thirty!

Without noticing I had consumed a huge portion of soup and spiked my glucose like crazy.

I stopped eating but it was already too late.

I kept scanning in horror as my glucose level rose from 130 to 137, 139...141

There goes 25 bucks.

A glucose level chart with a spike

*A chart showing me losing $25*

Mad that I 'wasted' an insulin spike on something as innocuous as soup, I caved and ate a chocolate chip cookie. The cookie was delicious, but it caused another insulin spike and made me feel horrible just a few minutes later. I felt shaky, exhausted, and mad that I had messed up.

Despite the hiccup I wanted to finish strong, there was still money on the line!

I stuck it out and finished the month with 27/28 days complete.

Interesting tidbits about my glucose levels

Wearing the continuous glucose monitor was really interesting! Every time I scanned it with my phone I felt like some kind of transhumanist cyborg.

I learned a few things that I wouldn't have been able to without the CGM:

  • Just before waking, my glucose levels drop. I could see this even when I took naps!
  • My glucose levels rise from lifting weights
  • I can get away with drinking a Guinness (not actually keto friendly)
  • The same food might raise levels differently in the morning vs the afternoon
  • Some foods I can get away with eating smaller portions, but a larger portion will send my glucose skyrocketing
  • The easiest way to keep my levels from spiking was to include a fat and/or a fiber source with my meal.

Meta-Takeaways: Optimality vs. Adherence

Is keto the best way to lose weight? Yes and no.

If I could snap my fingers and follow a diet, something close to the Renaissance Periodization diet is what I would choose. That's how I ate when I had six-pack abs and was competing in weightlifting. The RP diet is optimal. Every macronutrient is counted to the gram. Meals are spaced evenly throughout the day. Carbohydrate intake is adjusted based on exercise volume. Workouts feel great even when losing a ton of weight.

I had been trying RP since January 2019, but hadn't lost any weight! How could such an optimal plan fail me for so long?

Well duh, I couldn't stick with it.

The plan you don't stick to is a bad plan, no matter how good it is on paper.

Even though RP had worked well for me before, it wasn't working now, in my current situation. What worked in the past was great then, but it wasn't the best option right now.

For me, in my current situation, adhering to RP was hard. Adhering to keto was easy.

A few reasons why this challenge worked for me:

  • One simple rule: don't eat carbs
  • Group accountability
  • Monetary accountability
  • The number on the scanner kept me accountable by virtue of me wanting to check it every ten minutes.

Is keto the best way to lose weight? For me, right now, yes.

The next time you're crafting the perfect plan, think hard about how likely you are to actually follow through with it.

Was it worth risking $800?

Out of the initial $800, I got back $675. In the end I spent $125 for access to a Continuous Glucose Monitor, resources for eating a ketogenic diet, and a group to do the challenge with.

So was it worth it? Yes! I lost 8 pounds, learned a lot about what kind of nutrition plans work for me, and got to tinker with some cool tech.

twitter joke about horrible exchange rate

*Michael doesn't think it was a good trade*

If Justin runs this experiment again, and the situation is right for you, I'd recommend giving it a whirl.

What's Next?

I plan to continue eating keto until I reach my goal level of bodyfat. I'm curious to continue monitoring my glucose levels if I can get a hold of more GCMs.

I don’t plan on eating keto forever. I dislike how keto makes me feel while lifting weights, and eventually I would like more flexibility in my diet. When I’ve reached a certain level of leanness and maintained it for a time, I’ll ramp up the carb intake a little.

Thank you to Justin for organizing such a unique experiment, and for finally getting me to lose some fat.

Thank you to May for putting up with my horrible ketosis breath.

Would you risk $800 to do an experiment like this? Have you tried keto before? Let me know on Twitter or via email!