Are You Designed To Tolerate Caffeine? (It Might Be Written in Your DNA)

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Today’s Health Upgrade

• The big December bet

• Are you genetically wired for caffeine?

• The 60-second pantry test

• Fact or fiction: Does the Pomodoro Technique improve productivity?

• What everyone overlooks about “holiday weight” (it’s not what you think)

Arnold’s Corner
We’re Breaking The Rules (Again)

I told you we are different.

And you told us that you loved how we offered to pay you back 50% of your annual membership when you join The Pump Club app and finish our 90-day Foundation program.

Each program is customized for your fitness level, your goal, and whether you want to train with your body or gym equipment (including dumbbell only plans). It doesn’t matter if you’re 20 years old or 70, these programs meet you where you at, and help you get better every day.

The statistics on the people who took that deal give me hope. They’re starting their workouts at three times the rate of the average subscriber at a time of year when most people fall into the trap of letting their health slide. And the last month of the year is arguably the most important month for your long-term health.

So, since I care about your progress more than profit, I told the team to turn back on the offer for paying you back 50% of your membership when you complete The Foundation (you have 6 months to do it). At least through the end of December when most people gain their weight, but who knows?

I don’t have any consultants or board members to listen to, so if it keeps working to get you training, it might just stick around.

If you want to know why December is so important to your health, read Adam’s Corner today. This year, I want you to be different.

Health
Why Your Friend Can Drink Coffee at 8 PM (And You Can’t)

If you’ve ever wondered why one cup of coffee makes you feel alive while your coworker needs four just to function, you’re not broken — you’re built differently. And according to recent research, those differences go all the way down to your DNA.

Your caffeine tolerance is mainly genetic, and your best “dose” is the one your body responds to, not the one someone else can handle.

Scientists analyzed 26 studies, including more than 1.8 million people, to understand why caffeine hits everyone differently. The researchers found that variations in several key genes (especially CYP1A2, AHR, ADORA2A, and a handful of dopamine-related genes) lead to different caffeine habits and reactions. 

Depending on the version of the gene you inherit, your daily coffee consumption tolerance may shift by up to 32 percent per gene, and your metabolism speed can vary up to 60-fold. That’s not a typo. 

People with “fast” metabolism genes break down caffeine quickly, often needing more to feel alert. Caffeine can stay in the system longer for those with “slow” variants, which is why afternoon coffee can lead to a sleepless night. Genes linked to reward and sensitivity (like BDNF and SLC6A4) also explained 2–5 percent differences in cravings and how “good” caffeine makes you feel.

The researchers emphasized that this isn’t about discipline or tolerance training; it’s biology. While definitions of “dependence” can vary widely, the overall picture is clear: your DNA shapes how caffeine works in your brain and how long it sticks around.

If you’re unsure or don’t want to do a genetic test, experiment slowly and notice how timing, dose, and type (coffee, tea, espresso) change how you feel.

And if caffeine makes you anxious, it’s not weakness, it’s your wiring. If you’re sensitive to caffeine, here’s how to work with your biology, not against it:

• If you metabolize caffeine quickly, multiple small doses may work better than one big hit

• Stick to about 100 mg per day (about one small coffee).

• Avoid caffeine after noon to protect sleep.

• Try pairing it with L-theanine (found in green tea) to smooth the energy curve.

Together With SuppCo 
What Your Supplement Cabinet Is Hiding From You (And The 60-Second Test To Fix It)

We all have that cabinet. A few bottles we use every day, a few we meant to use, and a few we don't even remember buying.

Here's what most people don't realize: supplements are regulated as food, not medicine. That means companies don't have to prove their products work before selling them to you. Labels can say "supports immune health" without a single clinical result backing it up.

Your routine might be helping you, or it might be expensive dust. Independent testing labs consistently find problems most people never see, suggesting that up to 50% of supplements fail label-accuracy tests. 

Many use underdosed ingredients that are too weak to work. Others use cheap nutrient forms that your body can barely absorb. And every year, the FDA issues recalls for contamination or undeclared ingredients.

Pair that with an analysis by the U.S. Preventive Services Task Force of 84 studies on nearly 740,000 adults showing most vitamins and minerals don't deliver the disease-prevention benefits we imagine, and it becomes clear: the problem isn't supplements. It's not knowing which ones actually do what they promise.

The fix? Audit your routine. Instantly. For free. That's what SuppCo does. 

Scan any product, and you'll see whether it's properly dosed, whether the forms are clinically supported, whether it passes trusted quality standards, and if there's something better.

They've graded 30,000+ supplements using 29 evidence-based quality attributes. Their TrustScore tells you what's worth keeping and what's worth replacing.

What we love most: SuppCo doesn't sell supplements. No affiliate deals. No sponsored rankings. Just data so you can stop guessing and stop wasting money.

Here's the 60-second supplement test: go to SuppCo, grab the bottle you took this morning, scan it, and you'll have your answer before you finish your coffee.

SuppCo’s app is free, although PumpClub members can upgrade to their hyper-personalized Pro membership for 50% off using this link.  

Scan your routine. See what’s really working. And stop wasting money on supplements that don’t.

Fact or Fiction 
Does Taking Breaks Every 25 Minutes Boost Productivity?

The Pomodoro Technique is one of the most popular productivity methods around. And the core idea is simple: focus for 25 minutes, take a 5-minute break, and then get back to work, and you’ll have laser-like focus. 

The problem? The Pomodoro method is only partially supported by science, and the 25-minute rule isn’t magic. 

One study found that briefly switching your mental focus during a 50-minute task prevented the typical decline in performance that happens when you work continuously. The researchers proposed that momentarily "deactivating" your goal helps you stay locked in when you return to it.

But the specific 25-minute interval isn't based on rigorous research. A 2025 review found only three randomized controlled trials in the entire Pomodoro literature, with "moderate to low" overall evidence quality. And one study comparing Pomodoro to self-paced breaks found no significant differences in productivity or task completion.

The real secret: breaks work and help you stay mentally fresh, and can give you prolonged focus. The exact timing is personal. Start with whatever interval gets you moving, then adjust based on how you feel.

If breaks don’t seem to do it for you, here are four additional science-backed methods for increasing productivity:

Move during breaks: What you do on breaks matters. A brief 6-7 minute walk or stretch reduces fatigue more than passive rest, with benefits lasting 20+ minutes. Skip the phone scrolling.

Stop multitasking: Your brain can't actually do two things at once — it's just switching rapidly between tasks, which drains cognitive resources. People who frequently multitask perform worse on memory tests. Single-task instead.

Get outside: Nature uniquely restores attention. A 40-minute nature walk enhances executive function at a neural level compared to urban walking. Even 5 minutes of green exposure helps. When focus crashes, step outside.

Protect your sleep: No productivity hack compensates for sleep loss. Meta-analyses show sleep deprivation impairs attention, memory, and decision-making. Consistent sleep of 7+ hours improves working memory and focus. This is the foundation, and everything else is built on it.

Adam’s Corner
The Weight of a Single Pound

A few nights ago, long after the house was quiet and the kids had surrendered their last requests for water, I found myself standing in front of the refrigerator. Not to eat, but just staring, as if the soft hum of the motor had something to say.

It was the kind of moment that sneaks up on you in the last month of the year. You’re tired, you’re stretched thin, and your brain drifts toward the small, familiar negotiations: It’s the holidays. It’s been a long year. It’s fine.

And yet, for reasons I can’t entirely explain, that night the thought that arrived wasn’t about cookies or cocktails or stress. It was about a single pound.

A pound most people never feel.
A pound most people swear isn’t there.
A pound so small it seems impossible it could matter.

But it does.

Two weeks ago, in this newsletter, I shared research I haven’t been able to shake. Maybe you saw it. It was our weekly, “Number You Won’t Forget.” I thought that was a clever way to highlight stats, but maybe the title is prophetic: because I can’t get this one number out of my mind — and it’s not even the number I shared. 

One pound.

The number I shared in the newsletter was 76%. 

Maybe you skimmed it. Maybe it slipped into that category of “interesting health facts” that float around like dust; you notice them briefly, then go right back to your routine.

But it’s worth slowing down for this one.

Researchers weighed adults every six to eight weeks for a full year. They wanted to see when weight actually changes; not what people think happens, but what the data quietly records.

And here’s the twist that almost feels like a joke: During the holidays —between Thanksgiving and New Year’s — the average person gained one single pound.

Not five. Not ten. One.

But here’s the catch: the one pound you gain in the final month of the year made up 76% of total annual weight gain. And nearly no one lost that single pound. 

That pound just… stayed.
And the next year? Another one.
And the next? Same story.

If you’ve ever woken up a decade later and wondered how the scale crept up 10, 20, or 40 pounds, this is how. Not through crisis or catastrophe, but through consistency—the wrong kind.

How We Lose Our Balance

When I first read that study, I thought the explanation would be obvious. Stress eating. Office parties. Grandma’s stuffing. Travel. Booze. Cookies that seem to regenerate on the counter.

But the researchers found no single culprit.
Not stress.
Not travel.
Not the number of celebrations.

It wasn’t one thing. It was everything done just slightly differently.

The shift started in the mind, not the stomach.

Once the calendar flips to late November, we permit ourselves to lose balance. We move a little less. Sleep a little worse. Snack more often and pay less attention to hunger. We tell ourselves the season is a free space; an exception we’ll fix in January.

It’s not the indulgence that gets us. It’s the abandonment.

It’s the extra dessert and skipping your walk.
The late-night snacks and the lost sleep.
The celebrations and the resignation that the season is already ruined, so why bother?

During the year, we live with a natural ebb and flow.
Good weeks and bad. Wins and setbacks. Momentum and pauses. 

That’s normal. That’s human. That’s “balance.”

But the holiday mindset breaks that rhythm. It replaces the ebb and flow with an avalanche. A month where small decisions don’t cancel each other out — they compound in the same direction.

One pound doesn’t stick because it’s powerful. It sticks because we stop practicing the habits that help us return to center.

The Real Lesson Hidden in the Data

The moral of this story is not “be perfect during the holidays.” Please, don’t.

I’ll be the first to make sure you enjoy some dessert.
The first to pour you a drink, and then cheers you with a drink of my own.
The first to tell you to go to the party, stay too late, and laugh too loud. 

While I’m all about healthy behaviors, one of the healthiest things you can do is make memories instead of obsessing about macros.

But, at the same time, don’t lose your balance. Don’t throw away the tiny anchors that keep you steady the other eleven months of the year.

A 20-minute walk. A real breakfast. Drinking water before the wine. Paying attention to actual hunger instead of holiday autopilot. Moving your body a little every day, not as punishment, but as preservation.

You don’t need to prevent ten pounds. Just one.

You don’t need to overhaul your life. Just protect the little habits that keep you from drifting further than you want to go.

Because small changes lead to big results, but small abandonments do, too.
Both paths are built the same way: one decision at a time.

The question is which direction you want those decisions to take you. It’s why Arnold told us to turn back on our bet on you, where we pay you back 50% of your annual membership when you complete The Foundation. Because we want you to win December. 

As you step into the season, ask yourself a gentler, wiser version of the question we all pretend isn’t there: What would it look like to enjoy fully without losing yourself?

Because if one slight shift can pull you off course, one small choice made today can put you right back on the path you want to be on.

—

Publisher: Arnold Schwarzenegger​

Editors-in-chief: Adam Bornstein and Daniel Ketchell