Yeah, but you’re low-carb

This is something I hear a lot. I do share my clinical blood glucose data here from time to time, and many people (including myself sometimes!) marvel at how I keep my glucose “in-range”.

Since December 2020 I have not given myself boluses: letting my AID (Automated Insulin Delivery) system decide to give me insulin via basals and automatic boluses in the background.

Since the end of January 2021 I have not been telling my system about my carbohydrate intake. Yes, I no longer carb-count! Once I make it through the upcoming Christmas/NY season (and in fact through to Australia Day) I will have been doing this for a whole year.

I’ve written before about having a “fully” closed-loop system.
My BG stats have “loosened up” a bit with these changes but they’re still within levels that my doctors marvel at, and the quality-of-life improvements certainly make it worthwhile. I do use “temp targets” to optimise the way the system interacts with exercise such as some of my big bike rides, and I do keep a background eye on my CGM data (via my watch). But on the whole I just let the system get on with keeping my BG at a safe level.

But still I hear from people “Yeah but you eat low-carb, don’t you?”
Which continually amuses me! No, I don’t feel I do.

Do I eat “low carb”?

I have learnt a lot about eating over the years, and despite having to eat a gluten-free diet I do favour lower-GI foods and think of myself as probably “mid-carb”. But I do still indulge.

I have carb-counted in the past, and in fact am set up to track my food in detail. I found this very useful in 2019/2020 when I was losing weight as well as tuning my AID system. But I simply don’t usually bother now.

But prompted by a recent “low-carb” accusation I decided to fire up MyFitnessPal again and log all my food/drink for a day.

Food intake

Over the space of one day I apparently ate 193g of carbs. And 128g of protein. I did not try to limit (or increase) my carbs in any way this day, I just picked a day and recorded everything. I could continue recording over multiple days and get more of an average, but at this point I’m not sure it’s worth the effort. One average-feeling day seems appropriate.

I don’t know many people who would regard 200g of carbs per day as “low-carb”.

Certainly not “high-carb” compared to some people, but I’m sure people who think of themselves as eating “low-carb” would be horrified by the concept of eating 200g of carbs in just a single day!

It was neither an extravagant nor frugal day. Sure, I did eat some chocolate. But also plenty of home-cooked and fresh “whole” food. I do try to maintain a reasonably-healthy diet (while maintaining complete gluten exclusion).

My breakfast is probably the closest I get to “low-carb”. Yoghurt and strawberries (with some psyllium husk for fibre) was about 12g of carbs. But a long time ago I decided that after fasting my gut seems primed to absorb carbs quickly, so to avoid starting the day on a rollercoaster I tend to go for something lower-carb and with fibre to slow things down. Once that meal’s out of the way I’m not so picky.

BG response

min-max BG 3.5-10.0 mmol/L
Average BG 6.0 mmol/L (eHbA1c 5.4% if sustained)
Standard Deviation (CV) 1.2 (20%)
TIR for 3.9-7.8 mmol/L 92.8%
TIR for 3.9-10 mmol/L 98.3%

While it would have been nice if I hadn’t dropped below 3.9, it wasn’t really surprising. In the afternoon (after a late lunch that included chocolate pudding) I got carried away weeding in the garden (pulling out chest-high weeds: it had almost got out of control in that area of the garden) and carrying them down to the other end of the yard.

But I had forgotten to warn the system I was about to be exercising (I hadn’t planned on being out in the garden for more than a few minutes). By the time I finished and was back in the house I was dropping below 4, although a couple of glucose tabs fixed it. Ok, so I had one mini Snickers bar as well (because I could!).

But the rest of the day wasn’t too “rollercoasty”!

The sustained BG in the 7s after dinner can probably be partly blamed on the fats/protein in dinner’s grilled duck breast (my partner insists she’s almost got the process right, but we agree we’ll need to try again some time: “just to be sure” about the taste) along with some inactivity in front of the TV before retiring.

In fact, the previous day’s BG data was similar. With a late-night snack for a midnight spike:

Insulin use

Over the day my total insulin use was 38.88 U.

My average over the previous 7 days was 35.1 U/day (with a standard deviation of 5.0 U, so this day’s figure doesn’t seem exceptional).

Of course, keep in mind that at no point in the day did I tell my system what I was eating (or in fact that I was eating at all). I did not manually initiate any insulin boluses. I did replace my infusion site before dinner, and pause the pump while I had a shower earlier in the day, but those were the extents of my interaction with the system. I just got on with life.

All the insulin dosing happened quietly in the background:


How do I do it?

This is of course a 64 million dollar question.

My AID is running the standard oref1 algorithm (shared by OpenAPS, AndroidAPS, and FreeAPS X). The insulin activity/duration profile has been tuned to match the insulins I’m using, but the algorithm has not been modified. My configuration has been tuned and tweaked over months and years so I do trust it and its responsiveness. I do review my data occasionally, and on average every month or so end up tweaking settings to cater for my changing needs.

I am using Lyumjev insulin today which does help with the responsiveness, but I have got similar results with Fiasp (just with a little more variation) for most of 2021. Even Humalog and NovoRapid can work in a no-announce/no-bolus system, just with wider swings than some of us would want to live with.

My CGM is a Dexcom G6 (the sensor was 6 days old) and across the day it captured 96% of the 5-minute samples (the remaining 4% was back-filled after signal loss at times). Reliable enough that the system was able to respond to changes fairly promptly.


The bottom line

No, I don’t consider myself to be “a low-carber”.

“Mid-carb” maybe?
At least now I have a recent number to answer the question with.

10 thoughts on “Yeah, but you’re low-carb”

  1. Hi David. Thank you for this article. Only having been on a hybrid closed loop for 5 months a lot of what you said rings very true in my case as well. I also try to make healthier choices. I am learning to embrace that the odd indulgence is not a problem for me. I sometimes feel guilty about the amount of carbs I eat. I am slowly learning that what carbs I eat is what my body needs.

  2. Thank you, so interesting! No way I could achieve this using humalog. Is lyumjev easier to use in a pump compared to Fiasp? And any idea when lyumjev will be pbs listed? Can’t see anything online about it.

    1. You won’t see anything about it in Australia yet because it’s not get TGA-approved. And it’s only after that the ball can start rolling on PBS listing.

  3. Hi David, thank you – well covered as always! Interested to know more about Lyumjev, is it available on prescription now?

  4. This post gives me hope that we’re within sight of the holy grail – where the machines just do their thing and we don’t have to really think about it. Love it!
    Question: Do you have to change your pump sites more regularly because you’re using Lyumjev? I heard that was a thing for some pumpers using Fiasp…

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