When we study something in a research setting, we choose something that we hope will represent a larger group of that thing. If you want to know something about all roses, you study some roses. If you want to know something about people, you study some people. The group being studied is called the sample – it’s a sample of the larger group you want to know about. The size of this sample is called “n” in research studies. If you want to know something with a high degree of certainty you need big carefully designed studies with very large samples – big “n” values. These studies can help us identify what is most true for most people most of the time.

The problem is: these studies don’t tell you anything about the individual. The biggest, best, and most perfectly designed and executed studies tell us nothing about what will work for you or me or any single individual.

When this comes up I always think of this chart:


Don’t worry about what diets they’re comparing, that’s not the most important thing we’re seeing here. What’s most important is that the three columns in each of those graphs represent three different diets and each line represents one person who tried each of the three diets. None of those lines is level and none of them are the same. You can average the data and come up with one diet that is “better” but for some of those people it won’t be better. For some people, the “best on average” diet will be definitely worse  than the “worst on average.” It’s such an obvious thing to say: “people are different so the perfect diet must vary from person to person” and yet the dietary advice we’re given is pretty much exactly the same for everybody all the time. A little bit different for kids and pregnant and lactating women, a bit less for women generally than men, but otherwise pretty much all the same for everybody (every body) all the time.

Isn’t that crazy? We all know people who can eat more than we could dream of and will still bemoan their inability to gain weight. And we all know people who feel like they put on weight just by thinking about food. It’s crazy to think that the prevailing dietary advice for those two people would be basically the same.

The “low fat” Standard American Diet that I grew up on was making me fat and sick and miserable. After a lot of research and some preparation, it was time for my own experiment to find something that would work better for me, since what I had been doing clearly wasn’t working well at all. I started my own experiment on myself. I think this is the only way to approach our health: as our own experiment with an n of 1.



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