This Keto Life: The trouble with n=1

I recently returned from a wonderful ten day holiday in Indonesia, staying on the island of Gili Air and diving nearly every day (and I saw turtles on every dive. Only one shark this time though). While I’m on holiday, I don’t tend to eat keto, in spite of the damage this will cause. It’s just too complicated and difficult and two weeks won’t do a huge amount of damage.

Besides. Margaritas.

So I come back, having gained some water weight (and some non-water weight, because nom), and feeling sluggish and bloated, but hopefully not having given myself the usual long-term consequences (I did develop an abscess, probably due to increased inflammation – ugh – but it was tiny and I managed to blast it with antibiotics).

Here’s one thing that I find interesting: when I first went keto, my resting heart rate (RHR) went up. Not a huge amount, maybe 6 bpm, but it definitely increased from a stable point. I thought this was odd, but didn’t pay it too much mind.

Now, I have a Charge HR, and thus a continuous heart rate monitor. It’s true that it’s not the most reliable monitor, and also that the way it calculates “resting heart rate” is a little bit bogus (if you’re not moving, it thinks you’re resting. Maybe you are. But maybe you’re absorbing some profoundly stressful news, or reading an exciting book with cliffhangers. You see the problem).

The trends, however, are very reliable.

When I break keto, my RHR pounds to the sky, usually maxing out at about 73. When I get back on keto, it starts to plummet – my usual RHR (at least according to the Fitbit) sits somewhere between 57 and 60.

I am tempted to assume – and there is some good evidence for this – that this is because my body is now better adapted to a low carbohydrate, ketone-based metabolism, and so I run more efficiently when that’s in operation.

Here’s the problem: I’m one person, with a complicated body. There are a number of other things it could be.

It could be that my overall inflammation is lower when I’m on low-carb. This is well supported in the literature, and would interact with my Crohn’s (which is, after all, an inflammatory autoimmune condition).

It could be that I’m less anxious because I have predictable control over my diet (I plan a lot when I’m on keto and I find that comforting). The reason I don’t think that this is the case is that when I’m on holiday, I’m not stressed at all about food choices. I give myself free rein. All the same, it’s a plausible hypothesis that there is some underlying anxiety – I’m usually away from my home and my comfort zone and surrounded by strangers when I’m on holiday, so it wouldn’t be a surprise that my RHR is a bit elevated.

It could also be hormonal. I’ve noticed that my RHR is locked in very tightly to my hormonal cycle, and skyrockets around ovulation time, dropping off when the period arrives. And I did get my period about a day after I got home. So this is plausible – but again, it’s not always the case with the keto RHR changes.

What I suspect has happened is that going back on keto has lowered my inflammation, and that this has interacted with my hormonal cycle as well, because both of these things affect my RHR.

But I don’t know. I won’t ever know. Because there’s no way to test this with n=1. You’d need a wide sample of male and female people with active ileal Crohn’s disease, some of whom have adapted to a keto diet and some of whom haven’t, and then you’d need to monitor their RHR as they went on and off keto, to see if it changed, and how much.

This bugs me, because of who I am. I want to use it as supporting evidence that keto is good for me (I have a bunch of evidence for that already, but I get anxious, because it still is considered a really weird way to eat, and I get nervous when I stand out from the crowd, and already I have social anxiety around food choices), but I can’t be 100% sure (or even 95% sure with a basic p-value of 0.05) that this is what the relationship is, between ketone-based metabolism and cardiovascular efficiency.

The above is why I always narrow my eyes whenever anyone says “Well, [thing that is shown to be a placebo or worse] always works for ME.” Because maybe it does, and people do know their own bodies, but maybe it’s comforting, and anxiety is a factor, or maybe there’s something else that is correlated with that practice, and maybe…

Yeah. I’ve been told by a GP that perhaps I “over-science” my health.

All the same, it’s strangely fun.


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