The N-of-1 Problem
Browsing different websites, or if you’re old school, a bookstore-shelf or magazine rack, you’re going to be confronted with hundreds of different eating and exercise plans, all of which promise to be THE solution that gets you the results you’re after.
Which one is the best option for you? How do you choose? How do you know when you’ve found the right method? If something worked for your friend or relative, will it work for you too?
These questions are tricky because of the n-of-1 problem. What does that mean exactly?
Here’s a dot on a white background. Ignore all the other visual information on the rest of your screen. If the dot was the only thing in an infinite white blank space, what could you say about it?
Not much to say here. It's blue. It's a dot. N-of-1 is a tough situation to be in.
You can say it exists. You can say it’s blue. That’s about it.
You can’t say if it’s large or small. There’s nothing to compare it to.
You can’t say where it is in the infinite whiteness. There are no other dots to create coordinates against.
You can’t say whether it’s moving or still. There’s no background context to tell you about how it’s positioned in space.
You can’t say whether this dot is interesting, boring, beautiful, or any other subjective measure that relies on having some other dots to compare it to.
Look at all the new observations you can make just by having an n-of-2!
With just one more data point (the triangle) you can understand a lot more about the dot and its place in this white void.
The single dot is an example of the frustrations of dealing with a research condition where your number of subjects (n) is just one.
In an n-of-1 situation, you’re limited to at best, a bunch of educated guesses, and at worst, complete ignorance.
Life in the cosmos, for example, is an n-of-1 problem. We’ve never found any life or signs of life anywhere else in the universe. Are we alone? How unusual is life? How much rarer is intelligent life? Can you build life out of things besides DNA? There are lots of educated guesses, but until we have an n-of-2 or more, we’re stuck.
A lot of people also see themselves as stuck in an n-of-1 problem. Unless you have an identical twin, on this whole planet there’s only one genetic version of you (even twins will have different epigenetics and developmental pathways). As you go through life, you’re faced with a lot of choices about how to care for your body.
What food should you eat, and how much?
What foods disagree with your body and make you feel bad?
What kind of exercise keeps you trim and injury-free?
What kind of exercise do you naturally enjoy, so you can stick with it?
How much sleep do you need, and what helps you get good sleep?
What general principles do you need to follow to look and feel your best?
Nobody hands you a user’s manual with the answers to these questions. In fact, you find that there are thousands of people telling you they have the answers (often for a price), and many of those answers turn out to contradict each other!
And so we stumble into adulthood as lone researchers, trying to figure out how to make good choices in this high-stakes n-of-1 experiment. But all hope isn’t lost. Just as we can make educated guesses about life on other planets, there are some basic best-practices you can trust when it comes to taking care of your own body.
Let’s go over these ground rules!
1. The body isn’t easily knocked out of homeostasis.
Homeostasis is the tendency of a system to return to equilibrium. Think of a ball sitting in a bowl. You can drop the ball anywhere you like, but the curved edges on all sides will bring it back to the center of the bowl every time.
Your body has similar “curved sides”, in the form of multiple feedback systems.
As an example, let’s look at the pH level of your system (how acidic your body is).
If your body starts to become too acidic, you have systemwide proteins which soak up and store positively charged hydrogen. If you’re becoming too alkaline, free floating phosphate donates positive charge to bring you back. Your lungs can also dial up or down the amount of acidity by regulating the amount of CO2 in the blood. On a longer scale of several days, the kidneys can hold or release hydrogen to arrive at the right pH for normal function.
All of this balancing happens automatically, through the elegant biochemistry of life. Millions of years of evolutionary pressure created robust homeostatic systems. Perhaps a long time ago there was a mammal who had poor pH regulation. They died out quickly. But you’re still here.
Acidity is just one small example, there are thousands of points of homeostasis in the body, and they’re all just as stubborn.
Now, into this reality comes a product which promises to “reduce the body’s acidity” if you eat or drink it. At face value this sounds good. Who wants a body full of acid? But in truth, if it was that easy to change your pH with a single food, we would have died out long ago. Most of these types of products do nothing at all, but even in the case that they do move your pH, homeostasis will quickly rebalance it.
As you try to make choices about your n-of-1 body, remember that no one food, drink, or gadget will ever be a magic bullet, due to the strong corrective power of homeostasis. This will go directly against the sales pitch you’re given. Save your money and focus on eating normal, “real” food that provides your body the nutrients it needs to keep you stable and strong.
There certainly are conditions where the body falls out of homeostasis. These are diseases that require medical attention, because one of the corrective mechanisms inside you isn’t functioning correctly for some reason. This is when you need the help of a professional, not home-remedies or fly-by-night alternative healing products.
2. Your n-of-1 case is very unlikely to be an outlier.
If you talk to someone who believes in past-lives, you’ll find they never think they were a medieval peasant who died of typhoid at age 20. More often they were royalty, explorers, witches, or other interesting characters from history. It’s a natural human desire to be the interesting one, to be in the tiny percent of rare and remarkable cases.
People have the same bias when it comes to evaluating their body and its needs. It feels good to be one of the rare cases.
For example, in the past decade the issue of gluten intolerance has become a popular topic among health-conscious eaters. Ah ha! Perhaps the reason people feel so run down and bloated is because of all the gluten they’ve been eating!
We know that 1% of the population has a real issue with gluten. For them, when gluten reaches their small intestine, the body mounts an immune response, creating inflammation which causes all kinds of trouble through the digestive tract. This is known as Celiac disease.
However, even though someone might know there’s a low probability that they’re the 1 in 100 person with a gluten issue, they have a bias towards thinking we’re the outlier. It’s just more interesting.
Keep this in mind as food and fitness fads come and go. Many of these things will only apply to a small fraction of the population, which, statistically, you have an extremely low chance of being in.
Before working on obscure edge case interventions, make sure your basics are in place. This means frequent, light exercise and healthy food choices. This leads us right to our next point..
3. As you try different food and exercise methods, don’t leap to exotic conclusions at the expense of the more mundane.
Let’s continue with our gluten intolerance example. It’s quite common for people to give gluten-free life a try. They report that they’ve lost weight, sleep better, and have more energy. It seems gluten really was the problem all along!
What they don’t consider is that their gluten-free month saw a decrease in eating excess carbs in general, and eliminated processed food, beer, and other gluten-centric items. All of these things are much more likely causes of looking and feeling better.
If you misidentified gluten as the culprit, you’ve shut yourself off from a large variety of foods and made life more inconvenient for no good reason. You may think it was the gluten variable that mattered, but weren’t aware of all the hidden variables that came along with that choice.
This leads us to the next point.
4. Don’t introduce too many variables at once.
If you’re really interested in finding out what moves the needle for your health and fitness, be careful of the multiple variable problem.
For example, a person has been feeling run-down and lethargic, and is seeing body fat accumulate on their body. They decide enough is enough and embark on total lifestyle change. Starting on some arbitrary date, (January 1st is a popular one) they begin to eat better, stop drinking, go for a half hour jog everyday, and meditate in the morning.
A few weeks later they feel great, but have no idea what the main driver of the positive change was. Now they feel overwhelmed trying to keep up with so many healthy tasks at once and things begin to deteriorate.
A better approach is to think like the researcher you are. If you want to test a hypothesis for your n-of-1 body, introduce variables one at a time. Just add in the short daily jog for a month and see how you look and feel. Then try eating just right for a month. They try them together. This way of thinking takes patience and time, but will give you a ton of information in just a year of experimentation.
It feels good to get on a health kick and throw everything into the pot at once. After all, you want to feel better NOW, so why hold back? In the short term this works, but in the medium and long term it leads to burnout and yo-yo fitness. Stay cool and work on one variable at a time.
But for this to produce useful data, you’ll need to get the next point right.
5. Take good notes and track meaningful data.
In the experiment about what makes you healthy, you are both the scientist and the lab-rat. This presents an unusual problem, because when you think about how you’re feeling, you have to compare it to how you felt in the past, which is a state of being which you cannot access (because you’re currently feeling like you are now, not then).
Fortunately, you can take notes and capture data which preserves your past condition for your present self!
Keep a weekly or monthly log about how you feel. How was your sleep? How were your energy levels? How was your food and exercise? Looking back, you can start to see patterns emerge which you miss in the noise of daily life. Keep a notebook dedicated to this information, pen and paper often works better than digital for this kind of self-reflection.
In the same way, keep a monthly photo of your physique. You don’t even have to look at the photos, but there will be a day when you appreciate having this data about how your body was reacting to your life choices.
As far as data, there are only a few things which really matter for basic fitness. If you want good data track these things.
- Body fat
- Muscle mass
- Waist size/ How clothes fit
These days there are smart scales which connect to your phone and make logging this information easier than ever. The scales aren’t amazingly accurate, but they’re usually off by a consistent amount which at least shows your trajectory. Note that your weight isn’t a particularly useful number, and not something you should be orienting your fitness goals around. For more advice on how to best use a home scale this article is here for you!
6. Understand reversion to the mean.
We’ve been talking about the body as if it were a computer model we can run experiments on in isolation.
The messy reality is that your body is a living conversation with the environment it lives in, and the inputs it receives.
Let’s say you start swimming 3 times a week. In the first month you trim down and feel great. It seems like swimming is the solution! But in month two and three you don’t really see any additional physique improvement or higher energy levels. What’s up with that?
Reversion to the mean is what’s up. In all biological life, when a new stimulus is introduced, the biggest effects will be seen in the initial period of exposure. That first month of swimming is using new muscles, new neurological connections, all powered by new metabolic pathways. Psychologically, it’s also novel and fun!
But in month two and three the body has adapted to the swimming, and you stop getting big payoffs. At the same time the novelty has worn off and it starts to feel like a chore. Everything is reverting back to baseline.
Know that this will happen, and prepare for it. Because of reversion to the mean, no one thing will ever be a long term solution for fitness. But consistent effort will slowly raise your baseline, so that the “mean” is a higher and higher watermark lifting your health and happiness year by year.
7. Data about your n-of-1 body expires every seven years.
A final thing to consider in your self-research is that your body isn’t a static object. You’re aging, and with that aging certain things which used to work will stop working, while other methods that didn’t work will become effective.
We see this all the time at Kenzai, as someone in their mid-40s tells us, “When I was in my 20s I used to do this, can you make a plan that takes that into account?” The body of 20 years ago is history. It’s much smarter to let that stale data go and work with what you have now.
There’s no official timeline for this, but a good number to think about is seven years. This is a good compromise between 5 years (too short) and a decade (too long). Plus, it has a nice synchrony with the fact that nearly all of your cells will be completely replaced every seven yers. You’re literally a new person (except for some deep brain cells).
This means any intuitions you have about your body that are more than seven years old can safely be put aside. Starting from 18, this means you should think about a data-reboot at roughly 25, 32, 40, 47, 55, 62, 70, 77, 85, 92, and 100.
As you cross these thresholds, question your food and exercise choices. Is it time to try something different? Are there any beliefs you're holding out of habit instead of evidence?
Some examples might include the person who insists on continuing to run after their knees are shot, or the keto enthusiast who’s starting to see poor bloodwork come in after years of a meat-centric diet.
What worked before might not work now, and could even have negative consequences for your present body. These changes are often the hardest to accept, especially if your choices have become entwined with your perception of yourself (“I’m a runner” / “I don’t do carbs”). Be humble. Be flexible. And listen to what your body is trying to tell you!
Remember, there's no rush. You have 365 beautiful days a year to work on this experiment.
We see people put themselves under a lot of pressure to hit fitness targets by certain dates. “I want to lose 20 pounds by my 40th birthday”, or “I want to fit into this swimsuit by my summer vacation.”
The careful n-of-1 research outlined above goes directly against this impulse. Trying different foods and exercises for a few weeks, one variable at a time, and recording what happens seems like the slow way to get things done. But all that time is given back to you when you discover systems which work well for your use-caes. Then you really start cranking.
In the big scheme of things, is spending a year figuring out the best practices for your body really that long of a long time?
Best of all, this research doesn’t have to be a tedious grind! The fun of being the “1” in the n-of-1 is that you, more than anyone else on Earth, is the most interested party in how you look and feel. It’s fascinating work that YOU get all the benefit from. You have the time. You have the motivation. You have the smarts to get it done.
Let the research begin!
